Impact of Extraction Parameters on the Gallic Acid Content and Antioxidant Properties of Palo Prieto (Lysiloma divaricata) Fractions and Their Identification via UPLC-MS/MS.

Abstract

The palo prieto (Lysiloma divaricata) is a tree with grayish bark and pinnate leaves that is native to Mexico. This tree can reach heights close to 15 m and is a source of phytochemical compounds, including polyphenols. The optimized extraction method is important for preserving phytochemical compounds, particularly gallic acid. In general, solid-liquid extraction methods are the most commonly used methods for obtaining phytochemical compounds from Lysiloma divaricata. Herein, we report the results of a complex experimental design in which different parts of the plant (leaf, stem, and fruit) were used to investigate their antioxidant activities and gallic acid contents. In this design, we included variations in the type of solvent, time, and temperature. This method yields an extract rich in phytochemical components that may exhibit significant antioxidant activity, making it suitable for isolating natural antioxidant compounds. For these compounds, bromatological analysis, quantification of phenolic content, and identification and quantification of phytochemical compounds via UPLC-MS/MS identified 27 compounds, with gallic epicatechin, catechin, kaemferol-3-glucoside, procyanidin B1, and gallic acid as the major compounds. For the quantification of gallic acid by HPLC, the highest concentration of gallic acid was detected in the water-leaf-40 °C-90 min fraction. In addition, antioxidant activity via 1,1-diphenyl-1,2-picrylhydrazyl (DPPH), 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) was studied, and color measurements were performed. Additionally, the antioxidant activity of the fruit samples was evaluated via the DPPH method with an ethanol/water ratio of 30:70 % v/v at 60 °C for 60 min, which resulted in the highest percentage of inhibition. There was no significant difference in the antioxidant activity when ABTS was used between the samples. For the antioxidant activity determined via FRAP, the leaf sample exhibited the most significant activity when ethanol was used as the solvent at 50 °C for 90 min, with a value of 195,861 ± 44.20 µM eq Trolox/g DM. The phenol compounds of Lysiloma divaricata are promising sources of natural antimicrobials and antioxidants for potential applications in food packaging.