Bioactivity studies of different solvent extracts of partially defatted coconut testa obtained from selected coconut cultivars

Purpose: Coconut testa is a byproduct of coconut industry and is currently used for oil extraction. The partially defatted residue of testa is underutilized despite being able to convert into coconut testa flour (CTF). The objective of the present study was to compare the bioactivity of different solvent extracts of CTF obtained from selected Sri Lankan coconut cultivars namely, Gon Thambili (GT), Ran Thambili (RT), San Raman (SR), Tall×Tall (TT) and commercial hybrid (COM). Research Method: CTF of individual cultivars was sequentially extracted with hexane, ethyl acetate (EtOAc) and methanol (MeOH). The total phenolic content (TPC), total flavonoid content (TFC), ferric reducing antioxidant power (FRAP), DPPH radical scavenging activity, alpha amylase (Alpha-amy) and alpha-glucosidase (Alpha-glu) inhibitory activities were established in vitro using relevant assays. The phytochemical profiling of CTF was done using ultra high pressure liquid chromatography coupled with mass spectrometry. Findings: Among solvent extracts, MeOH extracts of all cultivars displayed significantly higher TPC, TFC, antioxidant and Alpha-amy inhibitory activities. GT exhibited the highest TPC (102.48 ± 3.46 GAE/g of crude extract), TFC (63.49 ± 4.47 CE/g of crude extract), FRAP value (1097.23 ± 1.24 µmol FeSO4/g of crude extract), DPPH radical scavenging activity (IC50, 45.37 ± 1.94 ppm) while TT resulted in the highest Alpha-amy inhibitory activity (IC50, 80.09 ± 4.67 ppm). The EtOAc extract of TT showed the highest Alpha-glu inhibitory activity (IC50, 7.82 ± 0.40 ppm). The distribution of phenolic constituents was found to vary among the different cultivars. Value: This study concludes that the extracts of CTF is a potent source of bioactive compounds that claim various bioactivities which can be used in developing functional foods.