Malvastrum coromandelianum Garcke, or Threelobe false-mallow
is a shrub belong to Malvaceae Family. It has been reported hypoglycemic
activity, antipyretic activity, affecting smooth muscle activity and ulceroprotective
activity (Andrade-Cetto and Heinrich, 2005; Dahanukar et al., 2000).
Staphylococcus aureus cause serious community-acquired and nosocomial
infection (Chambers, 1997). Epidemiological studies on high-level methicillin-resistant
S. aureus (MRSA), which is resistant to numerous antibiotics and
antiseptics, revealed nosocomial out breaks with clones dissemination
nationally and internationally. In 1961, there were reports from the United
Kingdom on S. aureus that had acquired resistance to methicillin
(methicillin-resistant S. aureus, MRSA) and MRSA isolates were
soon recovered from other European countries and later from Japan, Australia
and the United States (Enright et al., 2002). MRSA is now a problem
in hospitals worldwide and is increasingly recovered from nursing homes
and community. The methicillin-resistance gene (mecA) encodes a methicillin-resistant
penicillin-binding protein that is not present in susceptible strains
and is believed to have been acquired from a distantly related species.
In vitro antimicrobial screening in this study permits the selection
of crude plant extract with potentially properties to be used for further
chemical and pharmaceutical studies. The water extract from M. coromandelianum
Garcke was selected for antimicrobial activity testing against clinical
isolated of S. aureus, including MRSA strains. The objective of
this study was to assess the in vitro anti-staphylococcal activity
of the water extract from plant, M. coromandelianum Garcke.
MATERIALS AND METHODS
Malvastrum coromandelianum Garcke (Malvaceae) was identified
by Royal Forest department of Thailand and cultivated on January 2006
in open field at Singburi province, Thailand. Aerial part of plant was
collected in the beginning of June 2006 and the following extraction processes
were finished in the end of June 2006. The antimicrobial investigation
in this article was done on December of 2006.
The extraction method was modified from Chinese traditional method
(Lang and Wai, 2003). Dried aerial parts were collected and 10 kg of dried
plant was extracted by boiling in 100 L of water for 30 min. The extraction
was repeated twice. The pooled filtrates were spray-dried. The yield of
spray-dried extract powder was 8-10% w/w of raw material. In this study
used one batch of extraction and HPLC chemical finger print was determined
for each experiment to confirm the same quality of ME.
Tested microorganisms Twelve clinical isolates of S. aureus (supplied
by Department of Microbiology, Faculty of Pharmaceutical Sciences, Chulalongkorn
University, Bangkok, Thailand) were included in this study. The tested
isolates were divided into 2 groups, 6 of each, according to susceptibility
to methicillin where MRSA referred to methicillin-resistant strains and
MSSA referred to methicillin-susceptible strains. S. aureus ATCC
25923 and S. aureus ATCC 29213 were also used as reference strains.
MICs of crude water extract of ME were determined by agar dilution
method (Merck) (Lorian, 1996) while MBCs were determined by broth macro-dilution
method were (Lorian, 1996) and reference antibiotics Oxacillin (Sigma
Chemical Co., St.Louis, USA). Inoculates were prepared in the same medium
at density adjusted to 0.5 McFarland turbidity standard (108 colony-forming
units (cfu mL-1) and two fold dilution for the broth macro-dilution
procedure. The inoculated tube were incubated at 37°C and the MICs
were recorded after 24 h of incubation. The MIC was defined as the lowest
concentration of ME or Oxacillin at which the microorganism tested did
not showed visible growth while MBC was defined as the minimum bactericidal
concentration with negative subcultures on agar medium. Values were means
RESULTS AND DISCUSSION
Methicillin-resistant S. aureus (MRSA) is increased and caused
of nosocomial infection problem in many countries (Abrahamian and Snyder,
2007). Recently, only few antimicrobial agent including vancomycin and
teicoplanin are still effective against MRSA. Thus, this pathogen can
cause serious infection in various body systems in patients in particular
the ICU patients.
The screening of plant extract to inhibit growth of MRSA is during interesting.
Agar dilution and broth macro dilution were selected to evaluated in
vitro antimicrobial activity tests in this study. Due to the red brown
color of ME the MICs from only broth macro dilution was difficult to observed.
||Minimum Inhibitory Concentration (MICs) and Minimum
Bactericidal Concentration (MBCs) of ME against strains of S. aureus,
standard antibacterial agent: oxacillin
Therefore, agar dilution method was used to determine MICs of ME while
MBCs was from the broth macro dilution method. The water boiling extraction
methods which have been used for thousands of years in China to prepare
herbal remedies (Lang and Wai, 2003) was used in this study. Furthermore,
water was no toxic drug vehicle and less interfering effect on experiment.
The record of using of plant in family Malvaceae as medicinal plant has
been report such as in Turkey (Abu-Shanab et al., 2003), New Zealand
(Bloor, 1995) and Iran (Sharhidi Bonjar, 2004). The plant in Malvaceae
has been tested against MRSA for Althaea officinalis and showed
no inhibition effect against MRSA (Abu-Shanab et al., 2006).
Crude water extract of M. coromandelianum Garcke showed antibacterial
activity against MSSA (MICs = 2.5-5 mg mL-1, MBCs = 10-80 mg
mL-1) and MRSA (MICs = 2.5-5 mg mL-1, MBCs = 10-20
mg mL-1) as well as S. aureus ATCC 25923 and S. aureus
ATCC 29213. Although ME did not showed bactericidal activity to all tested
strains of MRSA (MRSA No. 6; MBC >160 mg mL-1) but it did
show inhibitory effect at considerable low concentration for crude water
extract against most of tested MRSA (Table 1).
This study is the first reported of antibacterial activity of M. coromandelianum
water extract. In addition the results from this study provide very
useful information concerning new natural drug discovery.
This study has been partly supported by grant year 2005 from graduate
school of Chulalongkorn University, Bangkok, Thailand. The authors would
like to show their appreciations to the staff of the Royal Forest department
of Thailand and of the Government Pharmaceutical Organization of Thailand
for their co-operations.