Phenolic compounds are considered the main bioactive components in okra fruits. In order to well understand the accumulation pattern of phenolic compounds in okra fruits during maturation, and to obtain okra fruits with high level of health-beneficial phenolic compounds, physicochemical properties, phenolic profiles, antioxidant capacities, and inhibitory effects on digestive enzymes of okra fruits at different maturation stages were investigated. Noticeable variations in physicochemical properties and phenolic profiles of okra were observed at different maturation stages. Phenolic compounds, including quercetin-3-O-gentiobioside, quercetin-3-O-glucoside (isoquercitrin), rutin, quercetin derivative, protocatechuic acid, and catechin derivative, were determined to be the major compounds in okra fruits, while quercetin-3-O-gentiobioside was the most abundant phenolic compound. Considering the accumulation patterns of fruit size, firmness, and total flavonoid content of okra fruits, the optimal harvest time of okra fruits with relatively high level of health-beneficial phenolic compounds was determined. Furthermore, okra fruits at different maturation stages exerted remarkable antioxidant capacities and inhibitory effects on the pancreatic lipase, α-glucosidase, and α-amylase. The Pearson's correlation showed that quercetin-3-O-gentiobioside was one of the major contributors to the antioxidant capacities and inhibitory effects on digestive enzymes. Results are beneficial for understanding of the accumulation pattern of phenolic compounds in okra fruits during maturation, and can aid in the targeting of specific maturation stages with an optimal phenolic profile for the production of health-beneficial products.
Keywords: Antioxidant capacity; Enzyme inhibition; HPLC analysis; Okra fruit; Phenolic compounds.