Browsing by Author "Witharana, S."

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Biosynthesis of silver and zinc oxide nanoparticles from Plectranthus zeylanicus for the development of antimicrobial formulations
(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) de Soyza, W.S.G.; Wijayaratne, W.M.D.G.B.; Napagoda, M.T.; Witharana, S.
With the emergence of microbial resistance to currently employed antimicrobial agents, the recent trend is to search for novel antimicrobial substances from nature. The traditional applications of plants and plant based products as well as metals and metalloids suggest the potential of these sources for the discovery of new antimicrobial compounds with diverse chemical structures and novel mechanisms of action. Moreover, it is reasonable to hypothesize that the metal nano-preparations produced from these plant extracts could offer highly potent antimicrobial properties due to the synergistic effect of the plant extract and the metal nanoparticles. Thus the aims of the present investigation are to evaluate the antimicrobial potential of pharmacologically underexplored Plectranthus zeylanicus (Iruveriya), a plant claimed as an antimicrobial remedy in traditional medicine and the green synthesis of silver and zinc oxide nanoparticles as effective herbal disinfectants. The antimicrobial activity of the n-hexane, dichloromethane, ethyl acetate and methanol extracts of P. zeylanicus was determined by disc diffusion and broth microdilution methods against Enterococcus faecalis, Staphylococcus aureus and Staphylococcus saprophyticus. The dichloromethane extract displayed a MIC value of 31.25 μg/mL against S. saprophyticus and S. aureus while a MIC of 250 μg/mL against E. faecalis. Therefore this potent extract was then utilized for the green synthesis of silver and zinc oxide nanoparticles by treating with AgNO3 and ZnSO4 aqueous solutions respectively. The formation of metal nanoparticles was monitored by the measurement of the absorbance of the reaction mixture within the range of 200-600 nm using an ultraviolet-visible spectrophotometer at different time intervals for a period of three days. The silver nano-preparation displayed high absorbance in the range of 240-260 nm and 420- 440 nm and the absorbance of the reaction mixture increased with time. Similarly, the Zinc oxide nano-preparation has shown a high absorbance at 350-370 nm. Products of the green synthesis were evaporated in hot air oven. The scanning electron microscopy was employed to study the morphology of the nanoparticles. The antimicrobial potential of the nano-preparations will be studied in detail for the development of potent and eco-friendly herbal disinfectant/s.
Determination of photoprotective potential in sunscreen formulations with different concentrations of Olax zeylanica (Mella) extract
(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Liyanaarachchi, C. E.; Napagoda, M.; Malkanthi, S.; Abayawardana, K.; Witharana, S.; Jayasinghe, L.
The ultra-violet (UV) component of the solar radiation can cause various deleterious effects on the human skin. The occurrence of wide range of dermatological diseases are correlated with the excessive exposure to UV radiation, out of which, skin cancers are more lethal than the others. Skin cancer is a result of chronic exposure to the UV radiation, but there are many acute effects such as hyperpigmentation, erythema and weakening of immunological functions. The best method to avoid UV exposure is to abstain from outdoor activities during the daytime, however, this is not always possible and practicable. Thus, the topical application of synthetic sunscreens has been widely adopted as a preventive measure despite the number of adverse effects associated with these products. In this respect, the development of herbal sunscreen products devoid of undesirable harmful effects as alternatives to the synthetic sunscreens would be highly beneficial. Therefore, the present study focuses on the development of herbal sunscreen formulations using different concentrations of aqueous-methanolic extract of Olax zeylanica and the evaluation of photoprotective potency in each formulation. The aqueous-methanol extract was prepared using dried leaves of O. zeylanica. Thereafter, sunscreen formulations were developed by incorporating this extract at different concentrations (ie. 25%, 50% and 75%) to the aqueouscream base. The UV absorbance of each preparation was measured between 260-400 nm and the sun protective factor (SPF) was calculated according to the Mansur equation. Calculation of SPF is an evaluation method of how much photoprotection is given by a sunscreen product and our observations revealed that the formulation with 25% of the extract possesses the lowest SPF. In the other end, the formulation containing 75% of the extract has the highest SPF which gives an indication that when the extract concentration is higher, the protection from UV radiation is also higher. The photostability of this formulation was also evaluated by calculating SPF after exposing it to the direct sunlight for 7, 14 and 21 days. Since there was no significant reduction in the SPF value within the stipulated time period, the formulation exhibited photostability. Based on the preliminary observations, it is possible to hypothesize the presence of UV absorbing organic molecules in the O. zeylanica extract. Therefore, experiments are in progress to identify these secondary metabolites and also to increase the efficacy and bioavailability of the formulation using nanotechnology.