Polyphenolic Compounds from Plantago lagopus L

Polyphenolic compounds constitute one of the most characteristic classes of compounds in higher plants. Cinnamic acid derivates (e.g. caffeic, ferulic and p-coumaric acid) occur widely in higher plants as ester or glycosides. Quinic acid and monocaffeates, especially chlorogenic acid, are the most widely present ester derivates. Besides, a large number of other simple esters and glycosides (mainly with glucose and rhamnose as sugar moie­ ties) of these phenylpropanoid acids have been de­ scribed. Only a few phenylpropanoid ester glyco­ sides which contain more than one sugar unit and a substituted phenylethanol moiety are known to date. Caffeic acid sugar esters have been shown to have antibacterial, antifungal, antiviral activity and inhibit 5-lipoxygenase (from the leucotriene biosynthesis). These compounds may also be inter­ est in plant pathology as natural plants protective agents and as repellent against herbivores (Ravn and Brimer, 1988). Moreover, rosmarinic acid and caffeic acid have shown a strong antimicrobial effect aginst selected plant pathogenic bacteria and fungi (Petersen et al., 1991). Rosmarinic acid, has been shown to in­ hibit 5-lipoxygenase, 3 a-hydroxysteroid dehydro­ genase, and lipid peroxidation and to have antinflammatory activity (Nakazawa and Ohsawa, 1998). On the other hand, Plantago plants have been used since ancient times as diuretic, an anti-inflammatory and an asthmatic drug in Asia and Europe (Nishibe et al., 1995), but the biologically active principles are still unknown. “Plantaginis herba” is listed in Japanese Pharmacopeia XI as an important crude drug and an aqueous extract is also used as a medicine (Nippon Koteisho Kyokai, 1986). In the course of a search for biologically active substances from Spanish plants, the phytochemical analysis of the aerial parts of Plantago lagopus L. revealed that it is a rich source of polyphenols of therapeutic interest, and a part of the possible bio­ logical activity of this species could be due to the polyphenolic compounds. In previous papers, we have reported the isola­ tion and structure elucidation of four iridoid glucosides from P. lagopus (Velazquez et al., 2000). Continuing our work on the constituents of this species, this paper deals with both the isolation and structure elucidation of plantamajoside (1), luteolin-7-O-monoglucoside (2), rosmarinic acid (3) and chlorogenic acid (4) from the aerial parts of the same plant. The compounds isolated were identified by means of spectral (UV, NMR) and chemical (acid and alkaline hydrolysis) evidence.