In vitro studies of antioxidant, antidiabetic, and antibacterial activities of Theobroma cacao, Anonna muricata and Clitoria ternatea

Abstract

The present study explored the total phenolic contents, antioxidant, antibacterial, and antidiabetic activities of four Indonesian plants, namely Theobroma cacao pod husk (yellow variant and purple variant of pod husk), Annona muricata leaves, and Clitoria ternatea flower. Antioxidant properties of the extracts and fractions were evaluated using a DPPH (2,2-diphenyl-1-picryl-hydrazyl) assay, and their antibacterial activity against Staphylococcus aureus and Escherichia coli by the microdilution method using resazurin as a colouring agent. The antidiabetic assay was performed by an α-glucosidase inhibitory activity using a glucosidase from Saccharomyces cerevisiae. The results revealed that the pod husk extract of T. cacao of both variants (yellow and purple) had good antioxidant activity and antidiabetic activity with IC50 as of 41.3 and 44.5 μg/mL for the DPPH assay, and 41.6 and 27.7 μg/mL for the α-glucosidase inhibitory assay, respectively. Meanwhile, for antibacterial test, T. cacao pod husk of both variants also possessed the most active extracts with MIC (minimum inhibitory concentration) as of 0.62 mg/mL against S. aureus. Moreover, the FTIR (Fourier Transform Infrared Spectroscopy) analysis suggested the presence of phenolic molecules containing in the extracts. This study revealed that T. cacao pod husk could be a potentially rich source of naturally occurring antibacterial, antioxidant, and antidiabetic medicine.