Content in phenolic compounds and antioxidant activity of extracts obtained from Amazonian plant species

The Amazonian Region has a great variety of medicinal plants with bioactive compounds and antioxidant activity, whose characterization could present some potential for sustainable development. The type of solvent influences the extraction and industrial application, considering the cost, solubility, and toxicity. The aim of this study was to determine the content of phenolic compounds and the antioxidant activity of aqueous extracts of Amazonian plants. The fresh leaves of an individual of Byrsonima crassifolia and Inga edulis were registered in the National System for the Management of Genetic Heritage and Associated Traditional Knowledge, No. AE536D5, and obtained from Embrapa, Amapa, Brazil. The vegetal species’ excicatas were identified by a taxonomist and deposited in the Amapaense Herbarium (HAMAB) under the codes 019453-HAMAB and 01945r-HAMAB, respectively. The geographic coordinates of collection sites were the following: Byrsonima crassifolia (N 0º23’16.73732”; W 0.387983), and Inga edulis (N 0°0’38.43551’; W 51.061070”). Fresh leaves were selected, washed, and dried in an air circulation oven at 60ºC for 4 hours. The dried samples were ground to obtain a particle size of approximately 5 mm. Extracts of the plant species were prepared by suspension of 1 g of the dry plant powder in 6 mL of water, at 30 ºC and 200 rpm for 1 h, followed by filtration using Whatman paper No. 4. The residue was then extracted by adding 6 mL of the water under the same condition. After this process, extracts were rotary evaporated under reduced pressure and lyophilized. The total phenolic (TP), total flavonoids (TF), total tannins (TT), and total proanthocyanidins (PROT) content and the capture of the DPPH and ABTS radical were determined using the method described by Maksimović et al. (2005), Zhishen et al. (1999), Maksimović et al. (2005), and Broadhurst, Jones (1978), Brand-Williams; Cuvelier; Berset (1995), and Re et al. (1999) respectively. All analyzes were performed in triplicate. The content of TP, TF, TT, and PROT was 700.54 ± 16.37 and 135.94 ± 1.22 mg of gallic acid equivalent/g of extract; 378.32 ± 8.68 and 31.70 ± 3.36 mg of catechin equivalent/g of extract; 1027.62 ± 40.59 and 98.39 ± 1.35 mg of catechin equivalent/g of extract; 91.54 ± 0.18 and 38.98 ± 1.76 mg of cyanidin equivalent/g of extract of Byrsonima crassifolia and Inga edulis, respectively. The TP and TF content obtained are higher than that found by Souza, et al. (2008) for hydromethanolic extract of the leaves of these plant species. The aqueous extracts of plant species showed high free radical scavenging capacity by DPPH and ABTS methods, 2666.19 ± 140.17 and 5513.10 ± 70.90 µMETrolox/g of extract of Byrsonima crassifolia; and 260.06 ± 7.64 and 845.91 ± 11.12 µMETrolox/g of extract of Inga edulis, respectively. Byrsonima crassifolia extracts have a higher content of phenolic compounds and antioxidant activity than Inga edulis, as observed by Sobrinho et al. (2020). The aqueous extracts of the studied plant species have a high content of phenolic compounds and good free radical scavenging capacity, using a low-cost and toxic solvent.