Phytochemical and pharmacological evaluation of tephrosa purpurea and eriosema psoraleoides on mating behaviour and isolated tissues

Abstract

The air dried and ground E. psoraleoides roots were exhaustively extracted with dichloromethane/methanol (1: 1) by cold percolation. The extract was partitioned between water and ethyl acetate. Chromatographic separation of the ethyl acetate layer led to the isolation of four compounds. These were identified as 4',5-dihydroxy-2',7-dimethoxyisoflavone (1), 4',5,7trihydroxy coumaronochromone (2), 4',7"-bisgenistein (3) and 4',5,7-trihdroxy-2'methoxyisoflavone (4). Similar treatment of the stem of T purpurea yielded four compounds, stigmasterol (5); lanceolatin B (6); semiglabrin (7); terpurinflavone (8); lanceolatin A (9). Of these, compound 8 i§ a novel compound. The characterization of these compounds was based on spectroscopic techniques (IH NMR, l3C NMR, 2D NMR, UVandMS). The crude extact of E. psoraleoides, T purpurea and some of the pure compounds were tested for smooth muscle and blood vessel relaxant activities. The methanol extract of the roots of E. psoraleoides (88 ug/ml.) had the highest relaxant effect (13 mm) on isolated aorta. The ethyl acetate fraction of the dichloromethane/methanol (1: 1) extract of T purpurea stem, stigmasterol (5), lanceolatin B (6) relaxed the aorta by 9 mm, 6 mm and 10 mm respectively. This indicates that E. psoraleoides and T purpurea may promote penile erection. The crude extract of E.psoraleoides (roots) had an insignificant effect on bronchial muscle where as the ethyl acetate fraction of dichloromethane/methanol extract of T purpurea and its pure compound semiglabrin (7) relaxed the bronchial smooth muscle by 1.5 ~L and 15~L respectively. The potent relaxant activity by semiglabrin (7) could be attributed to its aromatic groups. This probably explains the traditional use of T purpurea for the management of chest tightness. The methanol extract of the roots of E. psoraleoides (2.5 g/kg) was further tested for mating behavior on mice using yohimbine (360 mg/kg) and sildenafil (600 mg/kg) as a reference drugs. The results indicated that E. psoraleoides (roots) extract may promote erection. The crude extracts of E. psoraleoides, T purpurea and isolated compounds from T purpurea were also tested for antiplasmodial activities. The crude extracts showed antiplasmodial activities with ICso values of 9.33± 0.38 and 11.43± 0.47 ug/rnl for E. psoraleoides, and 10.47± 2.22 ug/rnl and 12.06± 5.53 ug/rnl for T purpurea, against chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum, respectively. The novel compound, terpurinflavone (9) showed highest antiplasmodial activity with an ICso = 2.73± 1.16 ug/ml and 1.36± 0.12 ug/rnl against W2 and D6 strains respectively. Laceolatin A (9) also showed significant activity against (06) and (W2) strains of P. falciparum with ICso value of 3.82 ± 1.00 and 3.82 ± 1.04flg/ml, respectively. The crude extracts of E. psoraleoides, T purpurea and some of the pure compounds isolated from T purpurea were further tested for antimicrobial activity. The crude extract of E. psoraleoides showed an inhibition zone of 12 mm against Candida albicans at a concentration of 1.8 mg/disc while the novel compound terpurinflavone (8) showed an inhibition zone of 16 mm against Microsporum gypsum at a concentration 50 ug/disc, The crude extract of T purpurea and the five pure compounds isolated from this extract were inactive against Staphylococcus aureus, Pseudomonas eruginosa, Candida albicans, Cryptococcus neoformans, Trichphyton mentagrophytes and Microsporum gypsum.