MOLECULAR PATTERN COMPARISON BETWEEN TWO PEDICULARIS SPECIES

In this work we report a comparison of the polar fraction composition between two Pedicularis species, namely P. verticillata L. and P. kerneri Dalla Torre, collected in the area of the Dolomites, Italian Alps, at an altitude comprised between 2000-2700 m a.s.l. The genus Pedicularis was traditionally comprised in Scrophulariaceae family but more recently was moved into the Orobancaceae, as well as other hemiparasitic species, on the basis of molecular data. Pedicularis species are mainly used in the Chinese folk medicine against several disorders like diuresis, exhaustion, collapse and senility. Little studies have been previously performed on P. verticillata evidencing the presence of neolignans, phenylpropanoids and iridoid glycosides while no references were available on P. kerneri, probably because of the relative inaccessibility of their habitat. The study of the polar fraction of P. verticillata led to the isolation and identification of seven compounds which were aucubin (1), euphroside (2), monomelittoside (3), mussaenosidic acid (4), D-mannitol (5) verbascoside (6) and echinacoside (7). The first four compounds are glycosidic iridoids while compound (5) is a chiral polyol frequently recognized in hemiparasitic species belonging to Orobanchaceae, i.e. P. viscosa and B. trixago and lastly compounds (6) and (7) are phenyl-propanoids. The co-occurrence of iridoid glycosides and phenylpropanoids have a chemotaxonomical importance. The composition of P. kernerii revealed the presence of iridoids like aucubin (1), euphroside (2), monomelittoside (3), mussaenosidic acid (4), plantarenaloside (8), 8-epiloganic acid (9), mannitol (5) and verbascoside (6) among phenyl-propanoids. It is interesting the presence in P. kerneri of 8-epiloganic acid (9) since it is considered a precursor of the other iridoids recognized in this species. Although in both cases we evidenced compounds already isolated from the genus, this study allowed us to show some similarities and differences between the two studied species. The first evidence is the different amount of iridoids in the two species with the major presence revealed in P. kernerii. Moreover, there are only two differences between the two phytochemical pattern: the further presence of plantarenaloside (8) and 8-epiloganic acid (9) in P. kernerii. As for the phenyl-propanoids, verbascoside was found in both Pedicularis while only P. verticillata showed also the presence of echinacoside. Moreover, we foresaw that the two studied samples presented a chemotype already recognized in species from Colorado as P. crenulata Benth; P. groenlandica Retz; P. procera Gray and P. racemosa Dougl. Ex Hook, characterized by euphroside (2) and aucubin (1) as main components. However the most interesting character was the presence of monomelittoside (2) actually never reported in this genus but previously found in species belonging to Lamiaceae family, as Melittis melissophyllum, but also in Plantaginaceae, and in Verbenaceae, Clerodendrum thomsonae Balf. f. All these families are comprised in the Lamiales order, and the co-occurrence of monomelittoside (2) is an evidence of the taxonomical affinity among these families.