Unveiling multifaceted bioactivity assessment of Psidium guajava and Azadirachta indica leaves extract as a potential natural tyrosinase inhibitors

Abstract

Tyrosinase is a critical enzyme involved in melanin production, playing a protective role against harmful ultraviolet radiation from the sun. However, excessive melanin synthesis can lead to dermatological issues, including skin irritation, redness, and hyperpigmentation. These conditions can be mitigated by employing tyrosinase inhibitors. Studies have demonstrated that aqueous extracts of Psidium guajava (guava) leaves and Azadirachta indica (neem) leaves exhibit significant tyrosinase-inhibitory activity. Specifically, Psidium guajava extracts have inhibition rates ranging from 68.58% to 79.51%, while Azadirachta indica extracts display 52.34%–56.48% inhibition rates. The antioxidant capacity of these extracts is closely linked to their total phenolic content. Fourier Transform Infrared Spectroscopy (FT-IR) analysis indicates that Psidium guajava extracts are abundant in polyphenols, including tannins and flavonoids, which contribute to their superior tyrosinase inhibition compared to Azadirachta indica. Moreover, GC-MS and HPLC analyses have confirmed the presence of biologically active compounds such as quercetin, gallic acid, vanillic acid, hydroquinone, caffeic acid, chlorogenic acid, rutin, catechin, sinapic acid, and ferulic acid, supporting the extracts’ anti-tyrosinase properties. Interestingly, the concentration of quercetin—a compound known for its antibacterial properties—is higher in Azadirachta indica leaves (45.42 ppm) than in Psidium guajava leaves (41.18 ppm). This higher quercetin content may explain why Azadirachta indica extracts demonstrate greater antibacterial activity despite their lower tyrosinase inhibition potential compared to Psidium guajava extracts.