Isolation, identification, quantification and antioxidant activity of secondary metabolites from coastal Brazilian herbs

Plantago catharinea, from family Plantaginaceae (which has pharmacological importance), arises coastal salt marsh ecosystems, specifically the zones of beaches and dunes [1]. It is considered a vulnerable species and endangered. The objective of this research was the isolation, identification, quantification and antioxidant activity of secondary metabolites from P. catharinea leaves. After fractioning by Gel Permeation Chromatography (Sephadex LH-20) 38 fractions were collected and submitted to TLC. The fractions obtained sufficient mass (more than 10 mg) were submitted to preparative HPLC and the isolated substances analyzed by NMR. Two isomers of molecular weight 639 u were identified. Differential characterization of these isomers was perceptible only by the analysis of nuclear magnetic resonance. The difference between these isomers is the position of the phenolic acid linked to the central ring of the glucose molecule. Both isomers have D-allose in your composition; there are many rare sugars in nature, while there are few abundant monosaccharides, such as glucose and fructose. D-allose is considered a rare sugar and it is defined as a monosaccharide in nature that there is little or limited amount. 2-(3,4-dihydroxyphenyl)ethyl-3-O-β-D-allopyranosyl-6-Ocaffeoyl-β-D-glucopyranoside (isomer 1), was elucidated for the first time in April 2012 in Plantago asiatica [3]. The quantification of these isomers was made by Mass Spectrometry. A calibration curve was obtained for the assay of the isomer 1 and 2 with a correlation coefficient of 0,973 using a/x weighting linear regression, with a 4.53% percentage of compounds. The antioxidant activity of these isomers is very different. The isomer 1 presents an activity similar to quercetin and gallic acid, while the isomer 2 presents low activity.

Keywords: Plantago catharinea, antioxidant activity, isolation

References:

Falkenberg, D.B. Aspectos da flora e da vegetação secundária da restinga de Santa Catarina, Sul do Brasil. Insula, 28: 1 – 30 (1999).

Amakura, Y.; Yoshimura, A.; Yoshimura, M. & Yoshida, T. Isolation and characterization of phenolic antioxidants from Plantago herb. Molecules 2013; 17: 5459 – 5466