Chemical composition and antioxidant capacity of Marrubium peregrinum L. from Vojvodina (Serbia)

Among Marrubium species only M. vulgare (white horehound) has been extensively investigated. Preparations of horehound are mainly used as expectorants and tonics with considerable benefit for chronic cough and asthma [1]. It is believed that the expectorant property is a result of the diterpenoid marrubiin which stimulates the secretions of the bronchial mucosa [2]. Four Marubium species had been recognized in Serbian flora [3], but there are no available data on their chemistry and biological activity, except for M. vulgare. In the present study, we report for the first time results on chemical composition (HPLC-DAD and HPLC/MS/MS) and free radical scavenger capacity (RSC) [4,5] of methanol extracts of M. peregrinum collected from four localities in Vojvodina. In order to simplify forthcoming results, we separated compounds maintained in methanol extracts into four groups on the basis of their polarity (by liquid-liquid extraction with chloroform, ethyl acetate, 1-butanol and water) [6]. Based on the HPLC-profiles, it is evident that the ethyl acetate fractions contain the majority of aglycones, but some flavone/flavonol glycosides and phenylpropanoids are present in both ethyl acetate and 1-butanol fractions (although in different ratios). The dominant compounds are: quercetin-3-O-β-D-glucoside, apigenin-7-O-glucoside, p-methoxy-cinnamic acid, kaempferol-3-O-β-D-glucoside, apigenin-7-O-(3''-p-coumaryl)-glucoside, isoramnetin-3-O-β-D-rutinoside, kaempferol, apigenin, quercetin. Chloroform and water fractions are very poor in phenolic compounds. The highest RSC was obtained for M. peregrinum ethyl acetate fraction regarding to both DPPH (IC50=9.4µg/ml) and NO (IC50=80.6µg/ml) radicals, which is in accordance with its chemical composition. Among tested standard substances (BHA, BHT, PG, rutin and quercetin), only rutin showed higher NO scavenger activity (IC50=30.8µg/ml) than ethyl acetate extracts.

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