Secondary Metabolites from Globularia alypum

Abstract

The genus Globularia (Globulariaceae) includes two species in Algeria. One of them is endemic, Globularia eriocephala (Pomel); the other Globularia alypum L., widespread in the Mediterranean region [1], is used in folk medicine. Its leaves are traditionally used as a hypoglycemic agent, laxative [2], cholagogue, stomachic, purgative, and sudorific [3]. In the present paper we report on the qualitative and quantitative analysis of secondary metabolites extracted from the medicinal plant G. alypum, which has been the subject of several chemical and pharmacological investigations [4–10]. Aerial parts of Globularia alypum L. were collected during the flowering season in eastern Algeria (April 2004). A voucher specimen for this material (VAREN/ SB BF Rv /04/04) was deposited at the Herbarium of the Faculty of Sciences, University MentouriConstantine. Air-dried and powdered aerial parts (1280 g) of G. alypum were macerated in an ethanolic solution (70%); the residue was filtered, concentrated, then successively extracted with petroleum ether, trichloromethane, ethyl acetate, and n-butanol. The AcOEt extract (10 g) was applied to a column of silica gel 60 and eluted with a gradient of CHCl3–CH3COCH3 with increasing polarity. Preparative TLC on silica gel 60 F254 using CHCl3–acetone–acetic acid (4:0.25:0.25) led to luteolin, para-coumaric acid, and cinnamic acid, while using CHCl3–acetic acid (4:0.25) led to apigenin. The para-coumaric acid and cinnamic acid have already been isolated from this plant [4, 5]. Flavonic compounds were identified using UV and 1H NMR spectra, chemical transformations, and comparison with authentic samples [11, 12]. Flavonoids 1, 2 have been isolated previously from another species of Globularia [13], but from G. alypum L. this was the first time. Apigenin, C15H10O5, mp 348–350°C, UV (λmax, MeOH, nm): 268, 335; +NaOH: 274, 324, 392; +AlCl3: 274, 300, 348, 382; AlCl3/HCl: 274, 300, 334, 380; NaOAc: 276, 306, 380. 1H NMR (250 MHz, CD3COCD3, δ, ppm, J/Hz ): 7.90 (2H, d, J = 8.7, H-2′, H-6′); 7.02 (2H, d, J = 8.7, H-3′, H-5′); 6.65 (1H, s, H-3); 6.55 (1H, d, J = 2.2, H-8); 6.26 (1H, d, J = 2.2, H-6). Luteolin, C15H10O6, mp 329–331°C, UV (λmax, MeOH, nm): 264, 350; +NaOH: 267, 329, 402; +AlCl3: 273, 303, 422; AlCl3/HCl: 274, 297, 358, 385; NaOAc: 254, 269, 352. 1H NMR (250 MHz, CD3COCD3, δ, ppm, J/Hz): 7.52 (1H, d, J = 2, H-2′); 7.49 (1H, dd, J = 8.4; 2, H-6′); 7.02 (1H, d, J = 8.4, H-5′); 6.62 (1H, s, H-3); 6.55 (1H, d, J = 2, H-8); 6.26 (1H, d, J = 2, H-8).