Phytochemical and biological investigation of Echium sericeum (Vahl) growing in Egypt

The genus Echium is represented in Egypt by seven species [1]. A number of naphthoquinones have been isolated from certain Echium species [2],[3]. The flavonoid constituents of certain Echium ssp. have been studied and a number of flavonoids were identified [4], as well as several pyrrolizidine alkaloids [5]. From the medical point of view, many Echium species are used in traditional Iranian medicine as tonic, tranquillizer, diaphoretic, cough suppressant and as a remedy for sore throat [6]. The present work deals with the study of the flavonoids of Echium sericeum and the evaluation of their insecticidal activity against Spodoptera littoralis (Boised) as well as the investigation of the anti-oxidant activity of both the total extracts and the isolated compounds, using the DPPH free radical assay. About 1kg of the aerial parts of E. sericeum were dried, powdered and extracted with petrol ether and then with 80% ethanol. After partition with chloroform, ethyl acetate and n-butanol the ethanolic extract yielded crude extracts containing flavonoids. These extracts were subjected separately to preparative paper chromatography (3MM, developed with 15% acetic acid) and the main flavonoid bands were cut and eluted separately with 90% methanol. The eluted fractions were further purified on a Sephadex LH-20 column. The isolated flavonoids were identified as apigenin, luteolin-7-O-rutinoside, apigenin-7-O-rhamnoside and quercetin-3-O-rhamnoside. Their identity was proven by TLC, PC, m.p., UV, ¹H-NMR and FAB-MS. The ethyl acetate and n-butanol fractions as well as the four flavonoids isolated from the plant showed a strong antioxidant activity in the DPPH assay. The petrol ether extract of E. sericeum showed the strongest insecticidal activity against S. littoralis, causing 71.5% mortality, whereas the butanol and 80% alcoholic fractions also had a marked effect causing 62.5% mortality at a concentration of 2.5%, respectively.

References: [1] Täckholm, V.(1974) “Students Flora of Egypt“ 2^nd Ed. The Anglo Egyptian Bookshop, Cairo University [2] Tabata, M.et al. (1982) Planta Med. 44: 234. [3] Fedoreev, et al. (1979) Khim. Prir Soedin, 62: 5. [4] Bandyukova, et al. (1970) Tr. Vses. Sezda Farm., 1^st Ed.: 253. [5] Culvenor, C.C.J (1956) Aust.J.Chem 9: 512. [6] Amin, Gh.(1991) Popular Medicinal plants of Iran. Bulletin Iranian Research Institute of Medicinal Plants, Tehran: 80