Antioxidant activity and phenolic compounds in three species of Passifloraceae (Passiflora edulis, P. Incarnata, P. Ligularis) from Guatemala

There is growing evidence that many diseases are caused by cellular oxidative processes involved in biomolecular damage, contributing to the etiology of chronic and degenerative diseases. Different phenolic compounds, such as flavonoids, are reported within the secondary metabolites in the Passifloraceae family, compounds associated with antioxidant activity. Three species were collected in different locations of Guatemala, Chimaltenango, and Suchitepequez and shade-dried. From these, dichloromethane and methanol extracts were obtained through percolation and concentration by use of rotary evaporator. P. incarnate methanol extract gave the highest yield (16.0%), while dichloromethane gave a lower yield (4.79%). Moreover, P. ligularis gave lower yields in methanol and dichloromethane (8.88 and 2.47%, respectively). This shows the great variety of metabolites that can be found in different species of the Passifloraceae family. Qualitative and quantitative assays for flavonoids were performed; qualitatively, five different bands of flavonoids were detected by thin layer chromatography (TLC), in which the presence of quercetin and routine in P. edulis and P. incarnate was detected. In the case of P. ligularis, however, any of the bands detected matched at any of the standards used. This indicates a variety of metabolites within each species of Passifloraceae. Quantitatively, flavonoid contents were expressed as rutin and vitexin, with P. incarnate containing the highest concentrations of 10.5 and 23.6%, respectively. The highest concentration of total phenolic compounds was found in both extracts from P. ligularis (31.93±1.67 and 30.80±2.49 μg/g, respectively). The antioxidant activity was determined qualitatively by TLC, where all the extracts showed positive activity. The spectrophotometric 1,1-diphenyl-2-picrylhydrazyl (DPPH) quantitative assay was used. This method allowed for the detection of the antioxidant activity of metabolites with polar characteristics. The methanol extract of P. ligularis presented the best antioxidant activity (IC50 1.65±0.07 mg/ml); lower activity was present in the dichloromethane extract of P. ligularis (IC50 5.48±0.13 mg/ml). Another quantitative method was the radical cation bleaching assay of 2,2’-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) reagent, with this method being the determinant of the antioxidant activity of metabolites with apolar characteristics. With this assay, the methanol extract of P. ligularis also presented the best activity (IC50 2.22±0.04 mg/ml); lower activity was present in the dichloromethane extract of P. ligularis (IC50 8.34±0.20 mg/ml). The trolox equivalent antioxidant activity (TEAC) was calculated, with the best results provided by the methanol extract of P. ligularis (12.39 mmol/g). This is consistent with the IC50 results of the DPPH and ABTS methods. These results demonstrated that P. ligularis gave the best antioxidant results, so this is why this native species should be studied further. The Passiflora species studied demonstrated antioxidant activity. This information, as well as the therapeutic uses attributed to this family, such as analgesic, antispasmodic, relaxing, and other uses, justifies the possible application of plants from this species in the cosmetic, food, or medicinal industries.