Phenolics content and antioxidant activity of two Asplenium species: life cycle-specific patterns

Abstract

Historically, ferns have been an important source of drugs, food, and fibers. Nevertheless, very few works have been done on their phytochemical characterization. Moreover, the haploid gametophyte phase of ferns has, probably due to the fragile structure, microscopic dimensions, and difficult collection, only rarely been the subject of phytochemical investigations. With the aim to support the ethnopharmacological importance of Asplenium species, the present work focuses on evaluating the phenolic content and antioxidant properties of sporophytes and gametophytes of Asplenium adiantum-nigrum L. and A. ruta-muraria L, two fern species widely distributed in Europe. Methanol extracts of gametophytes and sporophytes (fronds, rhizomes and roots) were subjected to UHPLC/DAD/(−)HESI-MS/MS analysis, and further to the evaluation of their scavenging capacities against ABTS•+ and DPPH•. Phenolics content and antioxidant activity of analyzed Asplenium species showed species-specific and life cyclespecific patterns. Identified phenolic compounds belong to the classes of phenolic acids (hydroxybenzoic and hydroxycynnamic acids), flavonoids (flavan-3-ols, flavonols), and xanthones. Sporophytes of A. adiantum-nigrum are especially rich in xanthones (mangiferin and mangiferin glycoside), potent bioactive compounds. Besides xanthones, gametophytes contain significant amounts of flavan-3-ols (epigallocatechin and epigallocatechin gallate). Flavan-3-ols are also recognized as the major phenolic compounds in both A. ruta-muraria sporophytes (gallocatechin gallate and epigallocatechin gallate) and gametophytes (gallocatechin and catechin). The excellent antioxidant activity of A. adiantum-nigrum rhizomes and A. ruta-muraria fronds, against both DPPH and ABTS radicals, could be ascribed to the high content of xanthones and flavan-3-ols, respectively. The results of the present study candidate these two fern species as potent antioxidant agents, thus supporting their traditional use.