Evaluating tyrosinase (monophenolase) inhibitory activity from fragrant roots of Hemidesmus indicus for potent use in herbal products

• MBALD is a fragrant methoxybenzaldehyde.
• MBALD is produced in Hemidesmus indicus root.
• This compound has significant inhibitory effect on monophenolase activity.
• Crude root extract of H. indicus showed monophenolase activity inhibition.

Root organs of Hemidesmus indicus are traditionally known for multipurpose medicinal applications. Root extracts of H. indicus contained 2-hydroxy-4-methoxybenzaldehyde (MBALD) as principal fragrant phenolic compound. This methoxybenzaldehyde was shown to have inhibitory potential against diphenolase activity of the tyrosinase. The present work explored the effects of this MBALD (both in crude extracts and pure forms) on the monophenolase activity. The lag time of reaction and the activity of monophenolase were affected upon supplementation of methoxybenzaldehyde. The increase in lag time indicated an inhibition of monophenolase activity which subsequently led to the reduction in total tyrosinase activity. MBALD was shown to be more potent than vanillin in inhibiting monophenolase activity. Inhibition kinetic analysis confirmed the same observation, with a higher Km value (0.395 mM) was determined for monophenolase reaction in presence of MBALD as compared to Km value of tyrosinase without any inhibition. As compared to pure MBALD, the crude root extract of H. indicus showed greater inhibition against monophenolase activity, which was also evidenced from the extension in lag time. This indicates its potential application in herbal products.