Nutritional characteristics, bioactive compounds and antioxidant potential of juá (Ziziphus joazeiro) fruits from Brazilian semiarid

Ziziphus joazeiro is a specie belongs to the Rhamnaceae family. These specie is a tree popularly known as “juazeiro” that occurs in the Brazilian semiarid caatinga biome. From this species, the local population use fruits called "juá" for production as jelly, jam, juice, and extracts of leaves, bark and roots as traditional medicines. Based on this popular application Z. joazeiro has become the target of some pharmacological studies. Juá can be considered a minor crop; thus, its fruits have not yet investigated in depth. The objective of this study was to evaluate the nutritional composition, phenolic compounds and antioxidant potential of the juá. The fruits used in these study were collected in four mesoregions from Paraíba: Agreste (AG), Borborema (BB), Mata Paraibana (MP), Sertão Paraibano (SP). All fruits in the same stage of maturation. The free phenolic (FP) were extracted by ultrasound used methanol/acetone. The conjugates phenolic (CF) were isolated by the acid extraction, followed by neutralization, partitioning with organic solvents. The FP and CF were separated RP-C18 column (100×4.6 mm, 3.5µm) and a C18 pre-column (12.6×4.6 mm, 5μm) using water and methanol acidified as mobile phases at a flow rate of 0.8 mL/min. The compounds were identified by comparing the retention times obtained with those of standards and the average area was used for quantification. Additionally, these extracts were evaluated antioxidant capacity using different in vitro assays. The juá from SP had the highest ascorbic acid content (17.96 mg 100g-1), total sugar (22.96 g 100g-1), total acidity (0.39 mg eq. citric acid 100g-1) humidity (72.61%) (p < 0.05). Twenty eight phenolic compounds were analyzed by HPLC-DAD, and fourteen phenolic belonging to different families of phenols were quantified. The flavanols were the majority families 70 - 80 %. The juá from MP reported the highest FP (25.90 mg 100g-1) different the others fruits SP (18.54mg 100g-1), BB (14.50mg 100g-1), AG (4.57mg 100g-1), (p < 0.05). The catechin (4.97 mg 100g-1), epigallocatechin gallate (12.04 mg 100g-1) and procyanidin B1 (3.28 mg 100g-1) were the predominant. Gallic (1.88 mg 100g-1) and caffeic (1.34 mg 100g-1) were predominant phenolic acid. The CF present highest content in juá from AG (26.06 mg 100g-1) (p < 0.05). Catechin (12.76 mg 100g-1), epigallocatechin gallate (5.76 mg 100g-1) and procyanidin B1 (5.48 mg 100g-1) were the predominant. The extracts not differ for the capture of the radical DPPH (381.74 - 349.32 uM Trolox 100g-1) (p > 0.05). However, these extracts from juá MP highest oxygen radical absorbance capacity (13480 uM Trolox 100g-1) and iron reducing capacity (2933 uM Trolox 100g-1). Pearson’s correlation showed that catequin, epigallocatechin gallate and procyanidin B1 present a strongest correlation with ORAC and FRAP assays. The geographical location was observed to interact and quantitatively govern the nutritional composition and phenolic compounds. This is an innovative study that shows the high potential juá fruits as sources of flavanols, which could be used in nutraceutical formulation, or incorporated into food products with functional properties.