Antioxidant and α‑Glucosidase Inhibitory Activities and Gas Chromatography–Mass Spectrometry Profile of Salak (Salacca zalacca) Fruit Peel Extracts

Background: Salacca zalacca or better known as salak fruit is widely distributed in tropical and subtropical countries, and it is traditionally used to treat diabetes. This study was aimed to investigate the salak peel extracts for their biological and chemical activities. Also, the chemical profile of the most promising extract was analysed on gas chromatography- mass spectrometry (GC-MS). Materials and Methods: The peel extracts were prepared by maceration process at room temperature with different ratio of ethanol/water. All the extracts were determined for their α‑glucosidase inhibitory activity using α‑glucosidase enzyme. The antioxidant activities of the extracts were determined through their Ferric reducing antioxidant power assay (FRAP) and 2,2-diphenyl-1- picrylhydrazyl (DPPH). The chemical constituents of salak peel extracts were analysed using gas chromatography–mass spectrometry (GC MS). Results: Phytochemical screening showed the presence of phenolic and flavonoid contents in all the extracts. About 100% ethanol extract shows the highest phenolic content (116.70 ± 0.764 μg/mL) while 60% ethanol extract has the lowest content 18.65 ± 1.155 μg/ml using gallic acid as a reference. 100% ethanol extract was observed to exhibit highest radical scavenging, ferric reducing antioxidant power (FRAP), and α‑glucosidase inhibitory activities (IC50: 49.45 ± 3.87 μg/mL, 144.81 ± 3.72 μg AAE/g, IC50: 11.62 ± 0.67b μg/mL), respectively. Water extracts had the lowest FRAP, radical scavenging activity as well as α‑glucosidase activity. The phytochemical investigation on GC‑MS showed the presence of active compounds in salak fruit peel extracts. Conclusion: Salak fruit peels showed the highest antioxidant as well as α‑glucosidase inhibitory activities. Phytochemical analysis on GC‑MS confirms the presence of gallic acid, linoelaidic acid, palmitic acid, α‑tocopherol, and steric acid which may contribute to α‑glucosidase inhibitory activity.