Exploration of nutritional, antioxidant and antibacterial properties of unutilized rind and seed of passion fruit from Northeast India

Passiflora edulis is an exotic fruit found in limited parts of India. The pulp of the fruit is mainly consumed while the rind and seeds are discarded. Thus, the present study aimed to investigate the physicochemical, nutritional, antioxidant and antibacterial properties of unused rind and seeds from yellow passion fruit (YPF) and purple passion fruit (PPF) collected from Northeast India. Physical investigation of biomass showed low ash and moisture content. Elements like K, Ca and Mg were the major macro elements present in both YPF and PPF rind and seed. A significant quantity of vitamin C, carbohydrate and reducing sugar was observed in the rinds, whereas total protein content was predominant in seeds. Methanolic extract of the rind of YPF showed the highest TPC and TFC followed by acetone extracts. High antioxidant activity (DPPH scavenging, ABTS (2,2-azinobis-3-ethylbenzothiazoline-6-sulphonic acid) and metal chelating) were displayed by methanolic and acetone extracts from rinds and seeds. The global antioxidant score was mathematically calculated to classify the best extract among the rind and seed samples. The presence of gallic acid, p-coumaric acid, ferulic acid, quercetin, myercetin and kaempferol in different extracts of YPF and PPF was confirmed from HPLC analysis. Gallic acid was found ranging from 17.52–83.00 mg/g, where flavonol glycosides were found ranging from 1.64–10.84 mg/g in both YPF and PPF rind and seed extract. Methanolic extracts of seeds showed the best antibacterial activity against gram-positive and gram-negative bacteria, followed by rind extracts. The obtained findings could help understand the nutritional and therapeutic values of passion fruit from Northeast India for their food and pharmaceutical applications.