Abstract:
Background: Since ancient times, traditional medicine has relied on the use of medicinal plants
to combat a range of infectious diseases. Plectranthus amboinicus and Plectranthus zatarhendi
(family Lamiaceae) have been utilized in traditional medicine in Sri Lanka as a remedy for skin
disorders, inflammatory conditions and microbial infections for a long period.
Objective: To evaluate the in vitro antifungal activity of crude extracts of P. amboinicus (Lour.)
and P. zatarhendi E. A. Bruce grown in Sri Lanka
Methods: The plants were authenticated and the aqueous and hexane extracts were prepared from
matured leaves and stems. For the extracts, the antifungal assay was performed against Candida
species (clinical isolate) and a fungal strain obtained from a clinical sample of pityriasis versicolor
patient. The assay was performed at two different concentrations of 500 and 1000 mg/mL by using
disk diffusion method and well diffusion method, respectively and each test was triplicated.
Ketoconazole was used as the positive control while distilled water and DMSO were used as the
negative controls. The zone of inhibition (ZOI) was measured and the results were analyzed by
One-way ANOVA test.
Results: At a concentration of 500 mg/mL, the hexane extracts of both plants displayed
significantly higher activity against Candida species compared to the aqueous counterpart by the
disk diffusion method. ZOI was not significantly higher in P. amboinicus compared to P.
zatarhendi. The highest ZOI at 1000 mg/mL was observed for the hexane extract of P. amboinicus
with a ZOI of 15.00±1.40 mm by well diffusion method. Interestingly the highest ZOI against the
fungal strain was obtained for the hexane extract of P. amboinicus (1000 mg/mL) with a ZOI of
17.36 ±1.55 mm by well diffusion method.
Conclusion: The study revealed that hexane extracts of P. amboinicus and P. zatarhendi
possessed a higher antifungal activity against Candida species and the fungal strain obtained from
pityriasis versicolor patient compared to the respective aqueous extracts.