|
Research Article
|
|
Biological Activity of Chemical Constituents Isolated from Streptomyces sp. Tc052, an Endophyte in Alpinia galanga
|
|
Thongchai Taechowisan,
Nantiya Chuaychot,
Srisakul Chanaphat,
Asawin Wanbanjob
and
Yuemao Shen
|
|
ABSTRACT
|
Some endophytic actinomycetes (120) were isolated from
the roots of Alpinia galanga. Identification of these endophytes
was based on their morphology and amino acid composition of the whole-cell
extract. Most isolates were classified as Streptomyces sp. (82),
with the remainder belonging to Nocardia sp. (11), Microbispora
sp. (3) and Micromonospora sp. (2). Eight isolates were unclassified
and 14 were lost during subculture. The strain identified as endophytic
Streptomyces sp. Tc052 strongly inhibited test microorganisms.
This endophyte was cultured, the agar was extracted with organic solvent
and the extract was purified on a column of silica gel to give a major
component, which was identified to be kaempferol, isoscutellarin, umbelliferone
and cichoriin on the basis of spectroscopic data. These compounds together
with the extract were tested for their antimicrobial activity against
bacteria and yeast using micro-dilution methods for the determination
of Minimum Inhibitory Concentrations (MIC) and Minimum Microbicidal Concentration
(MMC). The MIC values obtained with the crude extract varied from 64-128
μg mL-1 against tested microorganisms. All the isolated
compounds showed various activities.
|
|
|
|
How
to cite this article:
Thongchai Taechowisan, Nantiya Chuaychot, Srisakul Chanaphat, Asawin Wanbanjob and Yuemao Shen, 2008. Biological Activity of Chemical Constituents Isolated from Streptomyces sp. Tc052, an Endophyte in Alpinia galanga. International Journal of Pharmacology, 4: 95-101. DOI: 10.3923/ijp.2008.95.101 URL: https://scialert.net/abstract/?doi=ijp.2008.95.101
|
|
|
INTRODUCTION
Most plants are host to one or more endophytic microorganisms. By definition,
these organisms live between the living cells of their respective host
and cause no overt tissue damage. Usually, fungi are the most commonly
isolated endophytic microorganisms, but recently the endophytic actinomycetes
were isolated from the tissues of healthy plants (Shimizu et al.,
2000; Castillo et al., 2002). Some endophytes produced antimicrobial
agents that may be involved in a symbiotic association with a host plant
(Ezra et al., 2002; Castillo et al., 2003). We have recently
isolated endophytic actinomycetes from 36 plant species. The most prevalent
group of isolates were the Streptomycetes sp. occurring in 6.4%
of the tissue samples of Zingiber officinale. Some of the isolates
showed strong antifungal activity (Taechowisan et al., 2003). In
a separate study 59 endophytic actinomycetes were isolated from the roots
of Z. officinale and Alpinia galanga and tested against
some phytopathogenic fungi. The strain identified as Streptomyces aureofaciens
CMUAc130 showed the most effective antifungal activity (Taechowisan and
Lumyong, 2003). The major active ingredients from the culture filtrate
were identified as 5,7-dimethoxy-4-p-methoxyphenylcoumarin and 5,7-dimethoxy-4-phenylcoumarin
(Taechowisan et al., 2005). We report here the active constituent
isolation from the roots of Alpinia galanga Swartz (Zingiberaceae)
of another Streptomyces sp. Tc052. Extraction of the culture medium
of Streptomyces sp. Tc052 afforded kaempferol, isoscutellarin,
umbelliferone and cichoriin which displayed very strong antifungal and
antibacterial activities.
MATERIALS AND METHODS
Isolation of endophytic actinomycetes: Five hundred samples of
the root tissues of Alpinia galanga were collected from the environs
of Nakorn Pathom, Thailand, during the period April 2005-March 2006. Most
of them were healthy roots. The samples were washed in running tap water
and cut into small pieces of ca. 4x4 mm2. Tissue pieces were
rinsed in 0.1% Tween 20 for 30 sec, then in 1% sodium hypochlorite for
5 min and then washed in sterile distilled water for 5 min. Next the tissue
pieces were surface sterilized in 70% ethanol for 5 min and air-dried
in a laminar flow chamber. Finally the pieces were transferred to dishes
of humic acid-vitamin (HV) agar (Otoguro et al., 2001) containing
100 μg mL-1 nystatin and cycloeximide and incubated at
30 °C for 1 month. The colonies were inoculated onto International
Streptomyces Project-2 (ISP-2) medium (Shirling and Gottlieb, 1966)
for purification and stock cultures.
Antifungal activity of the actinomycetes isolates against fungi, yeast
and bacteria: The fungal pathogen Colletotrichum musae, the
causative agents of anthracnose of banana (the representative of hyphal
fungi of plant pathogen), was used for screening antifungal activity.
This fungal pathogen was obtained from Dr. Wipornpan Photita, Department
of Plant Pathology, Faculty of Agriculture, Chiang Mai University, Chiang
Mai, Thailand. It was grown on Potato Dextrose Agar (PDA). Mycelial disks
of 8 mm diameter were cut from the pathogen colonies and transferred to
the ISP-2 plates and positioned 6 cm away from each pre-grown actinomycete
colony. For antagonistic action to Candida albicans ATCC90028 (the
representative of budding yeast of human pathogen), the yeast was cultured
in ISP-2 broth at 30 °C for 24 h; the cells were diluted to 105
cells mL-1 in soft agar and then were overlayed on pre-grown
actinomycete colonies on ISP-2 plates. For antibacterial activity, we
used the solid media bioassay test against Staphylococcus aureus
ATCC25932, Escherichia coli ATCC10536, Pseudomonas aeruginosa
ATCC27853 and Bacillus subtilis ATCC6633. After incubation of the
selected actinomycete strains for 7 days at 30 °C on ISP-2 plates,
an agar disk was recuperated and placed on nutrient agar plates covered
by 3 mL of top agar containing 105 cells mL-1 of
bacteria test stains. The plates were incubated at 30 °C for 5-7 days
(for C. musae) and for 24 h (for C. albicans and bacteria).
The width of inhibition zones between the pathogen and the actinomycete
isolates was measured.
Identification of endophytic actinomycetes: Isolated actinomycetes
were observed for their morphological and biochemical characteristics.
For morphological characteristics, presence of aerial mycelium, spore
mass colour, distinctive reverse colony colour, diffusible pigment, sporophore
and sporechain morphology were recorded after 10 days incubation on ISP-2
medium. Diaminopimelic acid isomers and sugars from whole-cell extract
were analysed for chemotaxonomic studies (Becker et al., 1964;
Boone and Pine, 1968).
Extraction and purification of active compounds: Among the 120
isolates of endophytic actinomycetes, the isolate Tc052 was found to be
the best producer of antimicrobial substances. This isolate was selected
for extraction and purification of the secondary metabolites. Spores of
Streptomyces sp. Tc052 were used to inoculate 250 plates of ISP-2
and incubated for 14 days at 28 °C. The culture medium was then cut
into small pieces that were extracted with ethyl acetate (3x300 mL). This
organic solvent was pooled and then taken to dryness under rotary evaporation
to give a dark brown solid (5305 mg). The solid was separated by column
chromatography using silica gel 60 (Merck, 0.040-0.063 mm) and CHCl3:MeOH
(20:1, 20:2, 20:3, 20:4 and 20:5) as the eluent to give active fractions,
A-4 and A-5.
Antimicrobial screening: Quanlitative antimicrobial screening
was carried out using the disk diffusion assay as described in the protocols
of the US National Committee for Clinical Laboratory Standards (1997).
A single colony of C. albicans and bacteria was cultured overnight
in 10 mL Sabouraud broth (SB, for yeast) and nutrient broth (NB, for bacteria)
at 37 °C; after 12 h incubation, 0.5 mL of the culture suspension
was added to 4.5 mL pre-warmed SB and the solution was incubated at 37
°C to obtain cultures in the exponential phase of growth. The crude
extract and purified compounds to be tested was dissolved in methanol
(1 mg mL-1) and 50 μL was applied to sterile (6 mm diameter)
paper disks (Advantec, Toyo Roshi Kaisha, Ltd., Japan), dried and then
placed on Sabouraud agar plate spreading with C. albicans or placed
on nutrient agar plate spreading with test bacteria or placed on PDA plate,
each plate was then incubated with an agar block (8 mm diameter) containing
mycelial mats of the fungi in the center of the plate (the paper discs
were 2.2 cm from the fungi). Incubation condition was 37 °C for 24
h for bacteria and yeast and 30 °C for 72 h for fungi. Results of
the qualitative screening were recorded as the average diameter of the
inhibition zone surrounding the paper disks containing the test substances
and were reported. Each treatment consisted of three replicates. The experiment
was repeated twice.
Minimum Inhibitory Concentrations (MICs): MICs of crude extract
and purified compounds were determined by NCCLS microbroth dilution methods
(National Committee for Clinical Laboratory Standards, 1997). The crude
extract and purified compounds were dissolved in DMSO. A dilution suspension
of bacteria and yeast was inoculated into each well of a 96-well microplate,
each containing a different concentration of the test agents. We performed
doubling dilutions of the test agents. The range of sample dilutions was
256 to 0.50 μg mL-1 in nutrient broth supplemented with
10% glucose (NBG) (for bacteria) or Sabouraud glucose broth (for yeast)
and a final concentration of 1x105 cfu mL-1 of test
bacteria or yeast was added to each dilution. The plates were incubated
at 37 °C for 48 h. MIC was defined as the lowest concentration of
test agent that inhibited bacterial or yeast growth, as indicated by the
absence of turbidity. Test agent-free broth containing 5% DMSO was incubated
as growth control. Minimum Microbicidal Concentration (MMC) was determined
by inoculating onto nutrient agar plates (for bacteria) or Sabouraud agar
plates (for yeast) a 10 mL of medium from each of the well from the MIC
test which showed no turbidity. MMCs were defined as the lowest concentration
of test agent where was no microbial growth on the plates.
The fungal pathogen C. musae was tested for its response to the
crude extract and purified compounds using a Potato Dextrose Agar (PDA)
dilution technique. The purified compound (5.12 mg) was dissolved in DMSO
(1 mL), then serially diluted two-fold to obtain final concentration ranges
of 0.50-256 μg mL-1 in PDA. The medium (5 mL) was added
to a 5 cm diameter Petri dish. An 8 mm diameter plug of the fungi, removed
from the margin of a 4-day-old colony on PDA, was placed 1.5 cm from the
edge of the plate. Linear growth of the fungi at 30 °C was recorded
2 days after treatment. Each treatment consisted of three replicates.
The experiment was repeated twice.
RESULTS AND DISCUSSION
After 3-4 weeks incubation, the surface of some root tissue samples showed
hyphal growth which subsequently grew out onto the surface of the HV agar
(Fig. 1 ). Growth of bacteria and fungi from the root
tissues was almost completely inhibited by the antibiotics included in
HV agar leaving the actinomycetes clearly visible. The low level of bacterial
contamination observed was due to Bacillus sp. This contamination
may have arisen from spores on the surface of these tissues that were
resistant to chemical surface sterilization or may be due to an endophytic
Bacillus sp. (Bai et al., 2002). Incubation of surface-sterilized
plant parts in a moist chamber and plating of plant tissues on agar media
are techniques usually employed in plant pathology and not often used
in microbial ecology. However, they may be extremely useful in the isolation
of microorganisms from unusual habitats. Using these techniques, we were
able to confirm the presence of endophytic actinomycetes in plant tissues,
especially roots, where a large number of these organisms are most probably
found. The
|
Fig. 1: |
Growth of actinomycete colonies from sterilized blocks
of plant tissue on HV agar. This plate was photographed after 3 weeks
of incubation |
Table 1: |
Antimicrobial activity of endophytic actinomycetes isolates
against tested microorganisms |
 |
The potential of antimicrobial activity was evaluated
by the zone of growth inhibition on ISP-2 medium after incubation
at 37 °C for 24 h for bacteria and yeast and at 30 °C for
5-7 days for C. musae. Fourteen isolates were lost during subculture,
aS.a.: Staphylococcus aureus, E.c.: Escherichia
coli; P.a.: Pseudomonas aeruginosa, B.s.: Bacillus subtilis,
C.a.: Candida albicans, C.m., Colletotrichum musae, b4+:
Width of growth inhibition zone > 20 mm, 3+: 10-20 mm, 2+: 1-10
mm, 1+: <1 mm |
actinomycete isolates took at least 3 weeks to grow out from the tissues.
If the tissue sterilization procedure used in this study was not sufficient
to kill surface microbes, they would be expected to grow from specimens
within a few days.
Five hundred samples of the root tissues of Alpinia galanga yielded
at least 120 endophytic microorganisms. In total 120 isolates were recovered,
the majority of which were Streptomyces sp. (82), with the remainder
identified as Nocardia sp. (11), Microbispora sp. (3), Micromonospora
sp. (2). Eight isolates did not develop sporing structures, although meso-diaminopimelic
acid was detected in whole cell extracts, confirming an actinomycete status
and 14 were lost during subculture. The antimicrobial activity of endophytic
actinomycete isolates is shown in Table 1. The majority
of the isolates (>50) appeared not to produce secondary metabolites
which displayed antimicrobial activity against all of the test microorganisms.
The remaining isolates could be divided into five categories according
to the size of the growth-inhibition zones produced. This survey revealed
that only a small number was strongly inhibitory to test bacteria and
fungi. In a similar study, Sardi et al. (1992) obtained ca. 500
isolates from the roots of 13 plant species and most of these were
Streptomyces sp. They classified these isolates into 72 groups based
on their characteristics. After testing antimicrobial activity of 10 groups
against Micrococcus luteus and Fusarium oxysporum, then
found that all groups had antimicrobial activity against one or the other
organisms, but not to both. Thus most of their isolates had a narrow antimicrobial
spectrum. From the present study results of in vitro antimicrobial
activity (Table 1), only two endophytic actinomycetes
isolates had a strong potential of antimicrobial activity to S. aureus,
E. coli, P. aeruginosa, B. subtilis, C. albicans
and C. musae. These results demonstrated that some of endophytic
actinomycetes have the potential for inhibiting the growth of tested microorganisms.
An endophyte designated actinomycete Tc052 was of great interest, because
of its potent antimicrobial activity. Morphological observation of 3-day-old
cultures of Tc052 grown on ISP-2 medium revealed that sporophores to be
monopodially branched and flexuous, producing open spirals of oval-shaped
spores (1x1.5 μm) with smooth surfaces (Fig. 2 ).
The substrate mycelium was extensively branched with non-fragmenting hyphae.
The aerial mycelium was white changing to ash-grey with yellow soluble
pigment occasionally discernible. Based on results in morphological observation
(light microscopy and scanning electron microscopy) as well as on the
presence of LL-diaminopimelic acid in the whole-cell extract, endophytic
actinomycete Tc052 was identified as belonging to the genus Streptomyces.
Structure elucidation: Purification of A-4 fraction using 16-20%
MeOH in CHCl3 afforded 37 mg of compound 1 and 18 mg of compound
2 and purification of A-5 fraction using 12-16% MeOH in CHCl3
afforded 52 mg of compound 3 and 22 mg of compound 4.
Compound 1: Yellow crystals, m.p. 304-305 °C. UV λmax(MeOH):
370, 266 nm, (MeOH + NaOMe): 408, 277 nm, (MeOH + AlCl3): 400,
278 nm, (MeOH + AlCl3 + HCl): 400, 278 nm, (MeOH + NaOAc):
397, 277 nm. EIMS m/z (rel. abund. %): 286 (3) [M+, C15H10O6],
256 (7), 128 (100), 118 (33), 113 (67), 97 (95). 1H NMR (δ,
CD3OD): 7.09 (2H, d, J = 11.4 Hz, H-2`, H-6`), 6.74
(2H, d, J = 11.4 Hz, H-3`, H-4`), 5.95 (1H, d, J = 3.0 Hz,
H-6), 5.14 (1H, d, J = 3.0 Hz, H-8). 13C NMR (δ,
CD3OD): 144.3 (C-2), 136.8 (C-3), 170.9 (C-4),
 |
Fig. 2: |
Spores and hyphae of Streptomyces sp. Tc052.
Bar = 4 μm |
164.4 (C-5), 99.5 (C-6), 168.0 (C-7), 92.3 (C-8), 149.5 (C-9), 107.8
(C-10), 125.3 (C-1`), 130.9 (C-2`), 116.1 (C-3`), 158.6 (C-4`), 116.1
(C-5`), 130.9 (C-6`).
Compound 2: Dark yellow crystals, m.p. 300-301 °C. UV λmax(MeOH):
282, 332 nm. Degradation occurs with all shift reagents. EIMS m/z (rel.
abund. %): 286 (100) [M+, C15H10O6],
258 (47), 257 (9), 168 (80), 140 (52), 118 (38), 112 (5.4). 1H
NMR (δ, CD3OD): 7.06 (2H, d, J = 8.5 Hz, H-2`,
H-6`), 6.77 (2H, d, J = 8.5 Hz, H-3`, H-5`), 6.08 (1H, s, H-3),
5.59 (1H, s, H-6).
Compound 3: Colorless needles, m.p. 228-229 °C. It showed
intense blue fluorescence under UV lamp and gave a negative Molisch`s
test. EIMS m/z (rel. abund. %): 162 (8) [M+, C9H6O3],
149 (25), 138 (13), 121 (7), 110 (100), 94 (90), 81 (41), 66 (75), 55
(89). 1H NMR (δ, CDCl3 + CD3OD):
7.59 (1H, d, J = 15.8 Hz, H-4), 7.07 (1H, br.s, H-8), 6.97 (1H,
br.d, J = 8.1 Hz, H-6), 6.80 (1H, d, J = 8.1 Hz, H-5), 6.30
(1H, d, J = 15.8 Hz, H-3). 13C NMR (δ, CDCl3
+ CD3OD): 167.3 (C-2), 114.5 (C-3), 144.8 (C-4), 147.7 (C-4a),
114.7 (C-5), 121.2 (C-6), 144.2 (C-7), 113.4 (C-8), 145.3 (C-8a).
Compound 4: Transparent prisms, m.p. 215-216 °C. It showed
intense blue fluorescence under UV lamp and gave a positive Molisch`s
test. UV λmax(MeOH): 234, 289, 347 nm, (MeOH + NaOMe):
249, 306, 390 nm, (MeOH + AlCl3): 234, 289, 347 nm, (MeOH +
AlCl3 + HCl): 234, 289, 347 nm, (MeOH + NaOAc): 252, 282, 352
nm. EIMS m/z (rel. abund. %): 340 (2) [M+, C15H16O9],
320 (2), 293 (72), 179 (90), 178 (97), 167 (90), 149 (100), 127 (68),
97 (56). 1H NMR (δ, CDCl3 + CD3OD):
7.72 (1H, d, J = 9.5 Hz, H-4), 7.11 (1H, s, H-8), 6.94 (1H, s,
H-5), 6.19 (1H, d, J = 9.4 Hz, H-3), 4.88 (1H, d, J = 7.3
Hz, H-1`), 3.31-3.85 (m, 6H, H-2`-H-6`). 13C NMR (δ,
CDCl3 + CD3OD): 163.0 (C-2), 114.1 (C-3), 144.9
(C-4), 141.3 (C-4a), 113.3 (C-5), 148.9 (C-6), 149.8 (C-7), 104.7 (C-8),
149.99 (C-8a), 102.4 (C-1`), 76.0 (C-2`), 77.8 (C-3`), 74.0 (C-4`), 78.0
(C-5`), 61.7 (C-6`).
Compounds 1, 2, 3 and 4 were identified as kaempferol (Markham et
al., 1978), isoscutellarin (Jay and Gonnet, 1973), umbelliferone (Yamoguchi,
1970) and cichoriin (Abdel-Salam et al., 1986), respectively by
comparing their spectral data with those previously published (Fig.
3 ).
Results of the antimicrobial screening indicated that, the crude extract
showed a wide range of activity, being effective against bacteria, yeast
and fungi. Kaempferol and isoscutellarin showed strong activity against
Gram positive bacteria (S. aureus and B. subtilis), while
umbelliferone and cichoriin showed moderate activity. Kaempferol and isoscutellarin
exhibited moderate activity against Gram negative bacteria (E. coli
and P. aeruginosa), while umbelliferone and cichoriin showed weak
activity. Kaempferol, isoscutellarin and umbelliferone showed strong activity
against C. albicans and moderate activity against C. musae,
while cichoriin showed no activity against C. albicans and C.
musae (Table 2). The antibacterial and antifungal
activities of the crude extract and purified compounds were evaluated
and the results are shown in Table 3. In general, there
were differences in growth inhibition between compounds on various microbial
cultures. The crude extract and purified compounds showed both antibacterial
and anticandidal activities at tested MIC and MMC limit of 256 μg
mL-1 (Table 3). The MIC values obtained with
the crude extract varied from 64-128 μg mL-1 to tested
microorganisms.
 |
Fig. 3: |
Chemical structures of kaempferol (1), isoscutellarin
(2), umbelliferone (3) and cichorii (4) |
For compounds isolated from the crude extract, the MIC values lower or
equal to 128 μg mL-1 were obtained with compounds 1, 2
and 3 on all tested microbial species (100%), compound 4 on 1 (16.66%)
of the tested microbial species. Regarding the degree of activity of compounds
isolated from the crude extract, the lowest MIC value (16 μg mL-1)
was noted with compound 1 on S. aureus and C. albicans,
compound 2 on C. albicans. The results of the MMC determinations
indicated that the MMC values lower or equal to 256 μg mL-1
were observed with crude extracts on S. aureus and C. albicans
(40%). Within this tested interval (0.50-256 μg mL-1),
the MMC values were obtained with compound 1 (100%), 2 (80%) and 3 (40%)
of the tested microorganisms. The results of the MMC determinations indicated
that cidal effect of many of the tested sample could be expected. However,
a keen look of the results of MIC and MMC, showed that the MIC values
obtained are two-three times lesser than MMCs on corresponding microorganisms,
confirming the microbicidal effects of the concerned samples (Carbonnelle
et al., 1987).
Previous reports indicated that kaempferol, isoscutellarin, umbelliferone
and cichoriin were produced by numerous species of plants, including Combretum
erythrophyllum (Martini et al., 2004), Equisetum spp.
(Milovanovic et al., 2007), Scutellaria lateriflora (Gafner
et al., 2003), Teucridium parvifolium, Tripora divaricata
(Grayer et al., 2002), Arracacia tolucensis (Figueroa et
al., 2007) and Lomatia hirsute (Erazo et al., 1997).
The flowers of Impatients balsamina contain kaempferol which are
Table 2: |
Antimicrobial activity of crude extract and purified
compounds from Streptomyces sp. Tc052 |
 |
a: S.a., Staphylococcus aureus, E.c.:
Escherichia coli, P.a.: Pseudomonas aeruginosa; B.s.,
Bacillus subtilis, C.a., Candida albicans; C.m., Colletotrichum
musae, b0: No activity; 1+ (weak activity), 5-10 mm halo
diameter; 2+ (weak activity), 10.1-15 mm halo diameter; 3+ (moderate
activity), 15.1-20 mm halo diameter; 4+ (strong activity), >20
mm halo diameter |
known to possess antifungal, anticancer and antioxidant activities (Yang
et al., 2001; Wang et al., 2006). Kaempferol was a markedly
active inhibitor of transcriptional activation of COX-2 (Liang et al.,
1999) and have inhibitory activity against melanin synthesis (Lim et
al., 2006) and antibacterial activity against an acne-inducing agent
(Propionibacterium acnes) with MIC values in the range <32-64
μg mL-1 (Lim et al., 2007) and against Vibrio
cholerae and Enterococcus faecalis, with MIC values in the
range of 25-50 μg mL-1 (Martini et al., 2004).
While umbelliferone was weakly active against Mycobacterium fortuitum
and Mycobacterium tuberculosis (Figueroa et al., 2007).
Present study is the first in which kaempferol, isoscutellarin, umbelliferone
and cichoriin from culture of an endophytic Streptomyces species
was isolated from the root tissue of Alpinia galanga and we confirm
their antimicrobial activity against Staphylococcus aureus ATCC25932,
Escherichia coli ATCC10536, Pseudomonas aeruginosa ATCC27853
Bacillus subtilis ATCC6633 Candida albicans ATCC90028 and
Colletotrichum musae.
As stated in several reports, Streptomyces activity in plants
not only protects against pathogens, but the metabolic products of Streptomyces
also influence plant growth and physiology (Katznelson and Cole, 1965;
Mishra et al., 1987). As kaempferol, isoscutellarin, umbelliferone
and cichoriin has been isolated from endophytic Streptomyces sp.
Tc052 and their antimicrobial activity was observed. These results indicated
that some endophytic actinomycetes were potent for protection their host
from phytopathogenic microorganisms.
ACKNOWLEDGMENTS
This research was supported by Thailand Research Fund MRG5180173. The
authors are grateful to Mr. Y.N. He and Ms. H.L. Liang in Kunming Institute
of Botany (KIB), Chinese Academy of Sciences, for measuring NMR and MS
data, respectively.
|
REFERENCES |
Abdel Salam, N.A., Z.F. Mahmoud and F.K. Kassem, 1986. Sesquiterpene lactones, coumarins and flavonoids of Launaea tenuiloba Boiss grown in Egypt. J. Pharm. Sci., 27: 275-282. Direct Link |
Bai, Y., F.D. Aoust, D.L. Smith and B.T. Driscoll, 2002. Isolation of plant-growth-promoting Bacillus strain from soybean root nodules. Can. J. Microbiol., 48: 230-238. CrossRef |
Bai, Y., F.D. Aoust, D.L. Smith and B.T. Driscoll, 2002. Isolation of plant-growth-promoting Bacillus strain from soybean root nodules. Can. J. Microbiol., 48: 230-238. CrossRef |
Boone, C.J. and L. Pine, 1968. Rapid method for characterization of actinomycetes by cell wall composition. Applied Microbiol., 16: 279-284. Direct Link |
Carbonnelle, B., F. Denis, A. Marmonier, G. Pinon and R. Vague, 1987. Bacteriologie Medicale: Techniques Usuelles. SIMEP, Paris, ISBN: 2-85334-276-X.
Castillo, U., J.K. Harper, G.A. Strobel, J. Sears and K. Alesi et al., 2003. Kakadumycins, novel antibiotics from Streptomyces sp. NRRL 30566, an endophyte of Grevillea pteridifolia. FEMS Microbiol. Lett., 224: 183-190. CrossRef | Direct Link |
Castillo, U.F., G.A. Strobel, E.J. Ford, W.M. Hess and H. Porter et al., 2002. Munumbicins, wide-spectrum antibiotics produced by Streptomyces NRRL 30562, endophytic on Kennedia nigriscans. Microbiology, 148: 2675-2685. CrossRef | Direct Link |
Erazo, S., R. Garcia, N. Backhouse, I. Lemus, C. Delporte and C. Andrade, 1997. Phytochemical and biological study of Radal Lomatia hirsuta (Proteaceae). J. Ethnopharmacol., 57: 81-83. PubMed | Direct Link |
Ezra, D., U.F. Castillo, G.A. Strobel, W.M. Hess and H. Porter et al., 2004. Coronamycins, peptide antibiotics produced by a verticillate Streptomyces sp. (MSU-2110) endophytic on Monstera sp. Microbiology, 150: 785-793. CrossRef | Direct Link |
Figueroa, M., I. Rivero-Cruz, B. Rivero-Cruz, R. Bye, A. Navarrete and R. Mata, 2007. Constituents, biological activities and quality control parameters of the crude extract and essential oil from Arracacia tolucensis var. multifida. J. Ethnopharmacol., 113: 125-131. CrossRef |
Gafner, S., C. Bergeron, L.L. Batcha, J. Reich, J.T. Arnason, J.E. Burdette, J.M. Pezzuto and C.K. Angerhofer, 2003. Inhibition of [3H]-LSD binding to 5-HT7 receptors by flavonoids from Scutellaria lateriflora. J. Nat. Prod., 66: 535-537. Direct Link |
Grayer, R.J., N.C. Veitch, G.C. Kite, A.J. Paton and P.J. Garnock-Jones, 2002. Scutellarein 4’-methyl ether glycosides as taxonomic markers in Teucridium and Tripora (Lamiaceae, Ajugoideae). Phytochemistry, 60: 727-731. CrossRef |
Jay, M. and J. F. Gonnet, 1973. Isoscutellareine isolee de Pinguicula vulgaris. Phytochemistry, 12: 953-954.
Katznelson, H. and S.E. Cole, 1965. Production of gibberellin-like substances by bacteria and actinomycetes. Can. J. Microbiol., 11: 733-741. CrossRef | PubMed | Direct Link |
Liang, Y.C., Y.T. Huang, S.H. Tsai, S.Y. Lin-Shiau, C.F. Chen and J.K. Lin, 1999. Suppression of inducible cyclooxygenase and inducible nitric oxide synthase by apigenin and related flavonoids in mouse macrophages. Carcinogenesis, 20: 1945-1952. CrossRef | Direct Link |
Lim, Y.H., I.H. Kim and J.J. Seo, 2007. In vitro activity of kaempferol isolated from the Impatiens balsamina alone and in combination with Erythromycin or Clindamycin against Propionibacterium acnes. J. Microbiol., 45: 473-477. PubMed |
Lim, Y.H., I.H. Kim, J.J. Seo and J.K. Kim, 2006. Tyrosinase inhibitor from the flowers of Impatiens balsamina. J. Microbiol. Biotechnol., 16: 1977-1983. Direct Link |
Markham, K.R., B. Ternal, R. Staniy, H. Geigerand and T.J. Mabry, 1978. Carbon-13 NMR studies of flavonoids-III, Naturally occurring flavonoid glycosides and their acetylated derivatives. Tetrahedron, 34: 1389-1397. CrossRef |
Martini, N.D., D.R.P. Katerere and J.N. Eloff, 2004. Biological activity of five antibacterial flavonoids from Combretum erythrophyllum (Combretaceae). J. Ethnopharmacol., 93: 207-212. CrossRef |
Milovanovic, V., N. Radulovic, Z. Todorovic, M. Stankovic and Stojanovic, 2007. Antioxidant, antimicrobial and genotoxicity screeningof hydro-alcoholic extracts of five Serbian Equisetum species. Plant Foods Hum. Nutr., 62: 113-119. PubMed |
Mishra, S.K., W.H. Taft, A.R. Putnam and S.K. Ries, 1987. Plant growth regulatory metabolites from novel actinomycetes. J. Plant Growth Regul., 6: 75-83. CrossRef |
NCCLS, 1997. Reference Method for Broth Dilution Antifungal Susceptibility Testing of Yeasts; Approved Standard. 2nd Edn., NCCLS Document M27-A2. The National Committee for Clinical Laboratory Standards, Wayne, Pennsylvania, USA.
Otoguro, M., M. Hayakawa, T. Yamazaki and Y. Iimura, 2001. An integrated method for the enrichment and selective isolation of Actinokineospora spp. in soil and plant litter. J. Applied Microbiol., 91: 118-130. CrossRef |
Sardi, P., M. Saracchi, S. Quaroni, B. Petrolini, G.E. Borgonovi and S. Merli, 1992. Isolation of endophytic Streptomyces from surface-sterilized roots. Applied Environ. Microbiol., 58: 2691-2693. PubMed | Direct Link |
Shimizu, M., Y. Nakagawa, Y. Sato, T. Furumai and Y. Igaroshi et al., 2000. Studies on endophytic actinomycetes (I) Streptomyces sp. isolated from Rhododendron and its antifungal activity. J. Genet. Plant Pathol., 66: 360-366. CrossRef |
Shirling, E.B. and D. Gottlieb, 1966. Methods for characterization of Streptomyces species. Int. J. Syst. Evol. Microbiol., 16: 313-340. CrossRef | Direct Link |
Taechowisan, T. and S. Lumyong, 2003. Activity of endophytics actinomycetes from roots of Zingiber officinale and Alpinia galanga against phytopathogenic fungi. Ann. Microbiol., 53: 291-298. Direct Link |
Taechowisan, T., C. Lu, Y. Shen and S. Lumyong, 2005. 4-Arylcoumarins from endophytics Streptomyces aureofaciens CMUAc130 and their antifungal activity. Ann. Microbiol., 55: 63-66. Direct Link |
Taechowisan, T., J.F. Peberdy and S. Lumyong, 2003. Isolation of endophytic actinomycetes from selected plants and their antifungal activity. World J. Microbiol. Biotechnol., 19: 381-385. CrossRef |
Wang, L., Y.C. Tu, T.W. Lian, J.T. Hung, J.H. Yen and M.J. Wu, 2006. Distinctive antioxidant and anti-inflammatory effects of flavonols. J. Agric. Food Chem., 54: 9798-9804. PubMed |
Yamaguchi, K., 1970. Spectral Data of Natural Products, Vol. 1. 1st Edn., Elsevier Publishing Co., Amsterdam, London, New York.
Yang, X., D.K. Summerhurst, S.F. Koval, C. Ficker, M.L. Smith and M.A. Bernards, 2001. Isolation of an antimicrobial compound from Impatiens balsamina L. using bioassay-guided fraction. Phytother. Res., 15: 676-680. CrossRef |
|
|
|
 |