Antioxidant, antityrosinase and antibacterial properties of fresh and processed leaves of Anacardium occidentale and Piper betle

In this study, the antioxidant, antityrosinase and antibacterial properties of fresh and processed leaves of Anacardium occidentale (cashew) and Piper betle (betel) were analysed and evaluated. For assessing antioxidant properties (AOP) of total phenolic content, total flavonoid content, caffeoylquinic acid content, free radical scavenging activity, ferric reducing power and ferrous ion chelating ability, the Folin–Ciocalteu, aluminium chloride, molybdate, DPPH radical scavenging, potassium ferricyanide and ferrozine assays were used, respectively. Antityrosinase and antibacterial properties were determined using the respective modified dopachrome method and disc-diffusion method. The outstanding AOP of fresh cashew leaves far exceeded those of betel leaves, including temperate culinary herbs of rosemary, thyme and marjoram. Blanching resulted in a significant decline in AOP of cashew and betel leaves with leaching of phenolic compounds into the blanching water. AOP of microwave-treated leaves of cashew remained unchanged but leaves of betel exhibited significant increase. Tyrosinase inhibition of fresh cashew leaves was high while betel leaves exhibited an enhancement of tyrosinase activities. Blanching did not affect the tyrosinase inhibition of cashew leaves but microwave treatment resulted in significant increase. For betel leaves, tyrosinase inhibition remained unchanged. Results showed that fresh cashew and betel leaves inhibited both Gram-positive and Gram-negative bacteria tested. Blanched and microwave-treated cashew leaves exhibited strong antibacterial activity with those of betel leaves showed variable effects. Blanching water of cashew leaves also possesses antibacterial activity. The enhancement of tyrosinase activities of betel leaves, and leaching of bioactive compounds with antioxidant and antibacterial properties into the blanching water warrant further investigations.