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.
Citation
Degree of Master of SciencePublisher
University of Nairobi Chemistry
Subject
Phytochemicalpharmacological
tephrosa purpurea
eriosema psoraleoides
mating behaviour and isolated tissues