Abstract Book - 3rd International Symposium on Medicinal Plants ...

products are being used as a source of medicine since long. The medicinal properties of plants
have been investigated in the recent scientific developments throughout the world, due to their
potent antioxidant activities, no side effects and economic viability. Flavonoids and phenolic
compounds which are widely distributed in plants have been reported to exert multiple biological
effect, including antioxidant, free radical scavenging abilities, anti-inflammatory,… etc. Numerous
studies indicate that regular intake of polyphenol-rich beverages (Tea) and foods (Chocolate, Fruit,
and Vegetables) is associated with a protective effect on the cardiovascular system . Experimental
and clinical studies have also indicated that chronic intake of several polyphenol-rich natural
products is able to improve endothelial dysfunction and to decrease vascular oxidative stress
associated with major cardiovascular diseases such as hypertension. Experiments from our
laboratory with isolated arteries have shown that polyphenols cause nitric oxide (NO)-mediated
endothelium-dependent relaxations and increase the endothelial formation of NO. Thus, these
experimental and clinical studies highlight the potential of polyphenol-rich sources to provide
vascular protection in health and disease. There is a growing interest in the food industry and in
preventive health care in the development and evaluation of natural antioxidants from plant
materials. Some plants contain considerable amount of polyphenolic substances, which have been
reported to have antioxidant activity. These polyphenolic substances are also known as
proanthocyanidins (also referred to as procyanidisns) are one of the most beneficial groups of
plant flavonoids.
Key words: Antioxidant, free radicals, hypertension, Natural products, stress.
1.11 Evaluation of Combination Effect of Stilbenoid from Shorea gibbosa
with Vancomycin Against Methicillin-Resistant Staphylococcus aureus
(MRSA)
Basri Dayang Fredalina 1 , Azmi Abdul Muin 1 , Chan Kin Luoi 1 and Latip
Jalifah 2
1 School of Diagnostic & Applied Health Sciences, Faculty of Health Sciences, Universiti
Kebangsaan Malaysia. 2 Centre Of Chemical Science & Food Technology, Faculty of Science &
Technology, Universiti Kebangsaan, Malaysia.
<strong>Abstract</strong>: Stilbenoids have high potential in natural product research and pharmaceutical
industry. The aim of this study was to determine the effects of various stilbenoids from Shorea
gibbosa combined with vancomycin against methicillin-resistant Staphylococcus aureus (MRSA).
A total of nine stibenoid compounds, 5 stilbenoid dimers; Ɛ-viniferin, ampelopsin A, balanocarpol,
laevifonol and diptoindonesin G and 4 stilbenoid trimers; α-viniferin, johorenol A, ampelopsin E
and vaticanol G were evaluated for their antibacterial activities against two strains of MRSA; ATCC
33591 and Hospital Universiti Kebangsaan Malaysia (HUKM) clinical isolate. Minimum inhibitory
concentration (MIC) and minimum bactericidal concentration (MBC) for each active compounds
were determined using serial broth microdilution and plate streaking technique. Combination effect
of stilbenoids with vancomycin against MRSA was evaluated using checkerboard assay to
determine their fractional inhibitory concentration (FIC) index values. The MIC value of α-viniferin
on both MRSA strains was 0.1 mg/ml whereas the MIC value of johorenol A on ATCC 33591 and
HUKM strain was 0.1 mg/ml and 0.2 mg/ml, respectively. On the other hand, the MIC values of
ampelopsin E and vaticanol G were higher than 0.4 mg/ml. Out of five stilbenoid dimers tested,
only Ɛ-viniferin was capable of inhibiting the growth of both MRSA strains at MIC value 0.4 mg/ml.
The MBC value of Ɛ-viniferin showed bacteriostatic action against MRSA. The result of MBC
determination also showed that α-viniferin and johorenol A were bacteriostatic. Using
checkerboard assay, the FIC index value of Ɛ-viniferin in combination with vancomycin showed
the additive effect which was 0.5625. The combination effect of α-viniferin and vancomycin on both
MRSA strains and johorenol A-vancomycin combination against HUKM strain were also additive
(0.5< FIV ≤2.0). Only the combination effect of johorenol A and vancomycin against ATCC 33591
was synergistic (FIC