Antimicrobial Activities of Water and Methanol Extracts of Bitter Apricot Seeds
The aim of this study was to test the antimicrobial activity of the methanolic
extract of bitter apricot seeds. Bitter apricot seeds used in folk medicine
in the treatment of skin diseases and parasitic diseases. It been traditionally
used to treat parasitic infections and skin diseases. Water and methanol
extracts of bitter apricot seeds were screened against some bacterial
strains. Seeds were extracted by percolation method. Aliquots of the extracts
at variable concentrations were then incubated with different bacterial
strains and the antimicrobial activities of the water and methanolic extracts
from bitter apricot seeds were determined by MIC. Three antibiotics were
used as reference compounds for antibacterial activities. Bitter apricot
seeds extract inhibited significantly the growth of the tested bacterial
strains. Among the bacterial strains tested, Staphylococcus aureus
was most susceptibility. The highest antibacterial was exhibited by water
extract. Results from these findings suggest that this bitter apricot
seeds extract may be used as natural antibacterial for treatment of some
of diseases, especially local skin diseases.
In the past decade interest on the topic of antimicrobial plant extracts
has been growing. Use of herbal medicines in Asia represents a long history
of human interactions with the environment. Plants used for traditional
medicine contain a wide range of substances that can be used to treat
chronic as well as infectious diseases. A vast knowledge of how to use
the plants against different illnesses may be expected to have accumulated
in areas where the use of plants is still of great importance (Diallo
et al., 1999). The medicinal value of plants lies in some chemical
substances that produce a definite physiological action on the human body.
The most important of these bioactive compounds of plants are alkaloids,
flavanoids, tannins and phenolic compounds (Cai et al., 2004).
Bitter apricot (Prunes armeniuca) seeds (kernels) are by-products
of the apricot processing industry. They are used as a substitute for
bitter almonds to produce persipan for the bakery industry. The oil (53%
in the seed) is used, in e.g., cosmetics (Alpaslan and Hayta, 2006), as
a cheaper substitute for bitter almond oil. The seeds can also be of interest
as a food or feed ingredient because of their high crude protein content.
It contained approx. 21% (w/w) crude protein, 52% (w/w) crude fat, 1.5%
(w/w) crude fibre and 25.5% (w/w) carbohydrates based on dry matter. Bitter
apricot seeds originate from the variety Prunus armeniaca var.
amar (El-Badawy et al., 1994).
In general, bitter apricot seeds used in folk medicine in the treatment
of skin diseases and parasitic diseases.
The development of drug resistance in human pathogens against commonly
used antibiotics has necessitated a search for new antimicrobial substances
from other sources including plants (Erdogrul, 2002). Screening of medicinal
plants for antimicrobial activities and phytochemicals is important for
finding potential new compounds for therapeutic use. This study reports
the results of a survey that was done based on folk uses by traditional
practitioners in Iran for antimicrobial activity.
To our knowledge, antimicrobial activities of methanolic extract of bitter
apricot seeds have not been reported to date. In this study, we examined
the antimicrobial activity of bitter apricot seeds which have long been
used as a medicinal source in Iran.
MATERIALS AND METHODS
Fresh bitter apricot seeds were collected from the Arak villages, Iran
in June 2007.
Bitter apricot seeds extract was prepared by percolation method. The
plant materials were dried under shade and ground into fine powder using
electric blender. 50 g of dried powder was soaked in 50 mL methanol or
water for 2 h with intermittent shaking.
It was extracted with 80% methanol by percolation method. The extract
was collected and evaporated to dryness in a rotary evaporator. The antimicrobial
activity of water and methanolic extract were individually tested against
a panel of microorganisms, including Escherichia coli (PTCC 1330),
Staphylococcus aureus (PTCC 1431), Salmonella typhi (PTCC
1639), Salmonella para typhi A (PTCC 1230) and Salmonella
para typhi B (PTCC 1231) (Gram+ and Gram-). All microorganisms were
obtained from Pasture Institution, Tehran, Iran. Prior to the experiment,
working cultures were prepared by subculturing 100μL of each stock
culture in 9mL of Brain Heart Infusion agar (BHI, Merck) and incubated
37°C for 24h in order to obtain inoculate containing cultures in the
exponential growth phase of approximately 1x106cfu mL-1.
The Minimum Inhibitory Concentrations (MICs) of extract determined by
tube broth dilution. Briefly, geometric dilutions, ranging from 2 to 512μg
mL-1 of the methanolic extract, were prepared in tubes, volume
being 1 mL. Then 1 mL of BHI, was added onto tubes. Finally, 1 mL of 106
colony forming units (cfu mL-1) (according to Mc Farland turbidity
standards) of standardised microorganism suspensions were inoculated onto
tubes and the test was performed in a volume of 2 mL. Tubes were incubated
at 37°C for 24h. The same tests were performed simultaneously for
sterility control (BHI+test extract). Gentamycin, Oxacillin and chloramphenicol
were used as reference compound for antibacterial activities. Antibiotics
were reconstituted according to the manufacturers` directions, filtered
through a sterile 0.45-mm-pore-size polysulfone membrane and used the
same day. The MICs were considered to be the lowest antibiotic concentrations
(in micrograms per milliliter) at which there was no visible growth in
the wells. All tubes with no visible growth were subcultured by transferring,
in duplicate, 10 μL to sheep blood agar.
Dilution ranges for the reference method were from 1 to 512 μg mL-1.
The tubes containing 1 mL antibiotic dilutions were inoculated with 0.1
mL of a bacterial suspension in broth containing 106 cfu mL-1.
The inoculum was injected below the broth surface with a 1 mL pipette
first into the antibiotic-free growth control and then, by using the same
tip, into the tubes in sequence, starting with the tube containing the
lowest concentration of antibiotic and ending with the tube containing
the highest concentration of antibiotic. All tests were performed in duplicate
(National Committee for Clinical Laboratory Standards, 1985).
RESULTS AND DISCUSSION
Table 1 shows the minimum concentration of extract
required to completely inhibit the growth of five bacterial strains. The
relative growth of each microorganism after 72h of incubation in the presence
of different concentrations of bitter apricot seeds extract was compared
to the control. The MIC of the methanol extract of Escherichia coli,
Staphylococcus aureus, Salmonella typhi, Salmonella para
typhi A and Salmonella para typhi B were 128, 32, 64, 32 and
128 μg mL-1, respectively. The MIC of the water extract
of Escherichia coli, Staphylococcus aureus, Salmonella
typhi, Salmonella para typhi A and Salmonella para typhi
B were 64, 16, 32, 32 and 64 μg mL-1, respectively.
||MIC of against different bacterial strains
Water extracts exhibited a higher degree of antimicrobial activity as
compared with methanol extracts.
In 1830, Robiquet and Boutron-Chalard discoveredthe structure of the
HCN-liberating compound in bitter almonds(Lechtenberg and Nahrstedt, 1999).
Because the compound was isolated from Prunus amygdalus (synonym
Prunus dulcis), it wasnamed amygdalin. Amygdalin has subsequently
been found widespread in seeds of other members of the Rosaceae
like in apples (Malusspp.), peaches (Prunus persica), apricots
(Prunus armeniaca),black cherries (Prunus serotina) and
plums (Prunus spp.) (Franks et al., 2005; Conn, 1980; Frehner
et al., 1990). The diglucosideamygdalin was the first member to
be isolated of a new classof natural products now known as cyanogenic
glucosides. Cyanogenicglucosides are present in more than 2,500 different
plant species,including many important crop plants (Seigler and Brinker,
1993; Bak et al., 2006). Upon disruption of plant tissue containingcyanogenic
glucosides, these are typically hydrolyzed by β-glucosidaseswith
concomitant release of Glc, an aldehyde or ketone andHCN. This two-component
system, of which each of the separatecomponents is chemically inert, provides
plants with an immediatechemical defense against attacking herbivores
and pathogens (Conn, 1969; Nahrestedt, 1985; Jones, 1988; Morant et
al., 2003; Nielsen et al., 2006). In addition to their possible
defense function, accumulationof cyanogenic glucosides in certain angiosperm
seeds may providea storage deposit of reduced nitrogen and sugar for the
developing seedlings (Lieberei et al., 1985; Selmar et al.,
In this study, the water and methanol extracts from bitter apricot seeds
exhibited significant inhibitory effect on bacterial growth.
The most sensitive bacterium was Staphylococcus aureus, which
was inhibited by water extract. On the other hand extracts showed only
slight activity against Escherichia coli and Salmonella para
typhi B. Staphylococcus aureus have a single layer wall
as compared to Escherichia coli, Salmonella typhi, Salmonella
para typhi A and Salmonella para typhi B which
have a multi-layered structure.
All the same, given that water extract was effective then methanol extract.
Extract had lower antibacterial activity than gentamycin.
The active compounds present in bitter apricot seeds had a stronger and
a broader spectrum of antimicrobial activity. The antibacterial activity
may be indicative of the presence of some metabolic toxins or broad-spectrum
antibiotic compounds. Among those antimicrobial compounds, phenolic compounds,
terpenoids and alkaloids are very important components in antimicrobial
effects (Femenia et al., 1995; Brewer et al., 1994).
This study showed that bitter apricot seeds could be potential source
of new antibacterial agents and may be used as natural antibacterial for
treatment of some of diseases, especially local skin diseases.
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