Flavonols from Crude and Hydrolyzed Extracts of Anacardium Occidentale L. Leaf with Antimicrobial and Antioxidant Activities Against Skin Pathogens

The leaf of cashew (Anacardium occidentale L.) that was selected for this study, is traditionally used to treat skin diseases. The aims of the study were to investigate the antimicrobial (against skin pathogenic microbes) and antioxidant activities of the crude and hydrolyzed extracts, as well as seven flavanols that were reported to be found in the extracts. The activities were measured using micro-well dilution and antioxidant colorimetric assays, respectively. All the microbes excluding Malasseiza furfur ATCC14251 were inhibited by the extracts. The hydrolyzed extract was found to show higher activities than the crude extract. The highest activity with a minimum inhibitory concentration (MIC) of 125 µg/mL was indicated by both extracts against Staphylococcus epidermidis ATCC12228 and the hydrolyzed extract against Staphylococcus aureus ATCC12600, Micrococcus luteus ATCC4698, Corynebacterium minutissimum ATCC 23348 and Pseudomonas aeruginosa ATCC27853. The hydrolyzed extract was also found to inhibit two fungi that are Microsporum canis ATCC36299 and Tricophyton rubrum ATCC2188 with MIC of 500 μg/mL. Myricetin showed the highest activity against all the tested bacteria and yeast with the lowest MIC of 7.81 μg/mL in C. minutissimum. The hydrolyzed extract also showed greater primary antioxidant activities than that of the crude extract. Myricetin indicated good primary antioxidant activities with EC 50 values ranged between 2.23 μg/mL and 6.40 μg/mL. The highest secondary antioxidant activity was indicated by myricetin 3-O -rhamnoside. Thus, myricetin can be considered as the main contributor to the antimicrobial and antioxidant activities of the hydrolyzed extract.