Nutritional, chemical and functional potential of Inga laurina (Fabaceae): A barely used edible species

Abstract

Inga laurina is a plant species which produces edible fruits, and until now there is little information available concerning its nutritional, chemical and bioactive composition. In this study, we evaluated for the first time the proximate composition and mineral contents in its fruit (peel, pulp and seed), that is the traditionally consumed part. The seeds obtained the highest protein (19.52 g/100 g), carbohydrate (22.5 g/100 g) and mineral contents, mainly Cu, Cr, P, Mn, Se and Zn. The peel and pulp were excellent sources of fiber (4.5 and 11.05 g/100 g) as well as mineral content, with Cr and Cu standing out in the pulp. This study is notably the first to provide a detailed assessment of the nutritional compositions of traditionally consumed and not consumed parts of this fruit. Sensory analysis of the pulp was also performed, which indicated good acceptance. The antioxidant properties were characterized in the fruit, peels and leaves. The ABTS test showed that leaf supernatant hydroethanolic crude extract (EC₅₀ = 2.70 μg/mL) and its corresponding ethyl acetate (EC₅₀ = 1.68 µg/mL) and butanol (EC₅₀ = 2.48 µg/mL) partitions presented higher antioxidant potential compared to the control Ginkgo biloba (EC₅₀ = 12.17 µg/mL). The most active precipitate extract regarding DPPH was from the peel (EC₅₀ = 13.30 μg /mL) and the most active partition was the ethyl acetate (EC₅₀ = 13.37 μg/mL), both with better activity compared to the control Ginkgo biloba (EC₅₀ = 46.97 μg/mL). The ethyl acetate partition (EC₅₀ = 13.45 μg/mL) and butanol partition (EC₅₀ = 7.97 μg/mL) from the leaves showed the highest antioxidant capacity. Thus, extracts and partitions from the peels and leaves were studied from a phytochemical point of view due to presenting the best results for antioxidant capacity. The presence of phenolic compounds such as myricetin-3-O-rhamnopyranoside, myricetin-3-O-(2″-O-galloyl)-rhamnopyranoside and myricetin-3-O-(2″,4″-di-O-galloyl)-arabinopentoside-methyl ether were observed in the leaf crude extract and polar partitions, being reported for the first time in the Inga genus and Fabaceae family. Moreover, quercetin, quercetin-3-O-galatoctoside, quercetin-3-O-rhamnopyranoside, quercetin-3-O-(2″-O-galloyl)-rhamnoside, and quercetin tri-hexose were identified in the peel crude extract and ethyl acetate partition, in which the galloyl derivative of quercetin was identified for the first time in I. laurina fruit peels. GC-MS enabled separating and identifying substances such as palmitic and stearic acids, and ethyl oleate. It is possible to conclude that I. laurina pulp can be a supplementary food as a source of phenolic compounds, and the other organs of the plant (leaves and peel) are rich in flavonoids with great antioxidant capacity, making this species a promising source of antioxidants.

Keywords: Antioxidant; Edible fruit; Flavonoids; Inga; Minerals; Proximate composition.