CHARACTERISATION AND EVALUATION OF PHARMACOLOGICAL ACTIVITIES OF GEDUNIN FROM Entandrophragma angolense WELW. (MELIACEAE) AND GEDUNIN-2-HYDROXYPROPYL-β-CYCLODEXTRIN IN RODENTS

Abstract

Gedunin is a bioactive compound, obtained from Entandrophragma angolense (EA), which has antiplasmodial, antiproliferative and anti-allergic activity. However, poor aqueous solubility and first-pass effects limit its therapeutic usefulness. Cyclodextrins are cyclic oligosaccharides that form complexes with poorly soluble compounds, thus enhancing their pharmacological activity. This study was therefore designed to evaluate the pharmacological activities of gedunin-2-hydroxypropyl-β-cyclodextrin complex (GCD) in rodents. Gedunin was isolated from hexane extractive of EA heartwood by chromatographic methods. The structural elucidation was done using Nuclear Magnetic Resonance (NMR) spectroscopy. The stoichiometric ratio for complexation of gedunin and cyclodextrin was determined by UV-VIS spectrophotometry using Job's method of continuous variation. The GCD was characterised by Fourier Transform infra-red spectroscopy, ¹H-NMR and X-ray diffraction analysis. Fifty Swiss mice (20-25 g) were allotted into ten treatment groups (n=5): Groups 1-5 received 10% propylene glycol (PG 10 mL/kg), GCD (50,100, 200 mg/kg), Gedunin (50 mg/kg) orally for acetic-acid induced writhing test, Groups 6-10 were similarly treated for formalin-induced paw licking test. Sixty-five Wistar rats (180-220 g) were allotted into 13 treatment groups (n=5): Groups 1-6 received PG, GCD (50, 100, 200 mg/kg), Gedunin (50 mg/kg), and indomethacin (5 mg/kg) orally for carragenaan-induced paw oedema inflammation model. Groups 7-12 were similarly treated as in oedema model before carragenaan injection into the air pouch. Group 13 received PG but had no carragenaan. Twenty-four hours after carragenaan, pouch exudates were measured and leucocytes counts determined using microscopy. Nitric oxide, malondialdehyde, reduced glutathione (GSH) levels and myeloperoxidase activity in the fluid were determined using spectrophotometry. Tumour Necrosis Factor-alpha (TNF-α) level was determined by ELISA. A 4-day antimalarial test was carried out using thirty-five P. berghei infected Swiss mice (18-22 g) in Groups 1-7 (n=5): PG, GCD (50, 100, 200, 400 mg/kg), Gedunin (100 mg/kg), chloroquine (10 mg/kg). Data were analysed using descriptive statistics and ANOVA at α0.05. The NMR spectral details for gedunin were consistent with previously reported spectra. The stoichiometric ratio determination of GCD signified the formation of a 1:1 mole ratio stable inclusion complex. The GCD (200 mg/kg) significantly decreased writhing response (21.25±1.49) compared with equivalent Gedunin dose (50 mg/Kg) (25.80±1.07) relative to control (62.00±1.38). The GCD (200 mg/kg) significantly reduced licking duration (39.10±4.80s) compared with gedunin (71.60±7.97s) relative to control (81.70±3.84) in the inflammatory phase. The GCD (200 mg/Kg) significantly decreased oedema compared to gedunin (68.8% vs 60.0%) post-carrageenan. The exudate volume and leucocyte count were significantly reduced by GCD (200 mg/kg) (1.95±0.23 mL, 30.76±1.83) than gedunin (2.60±0.05 mL, 57.92±2.16) relative to control (3.250± 0.17 mL, 88.32±4.11). The GCD (200 mg/kg) significantly decreased myeloperoxidase activity and inhibited TNF-α release compared with gedunin and control. The carrageenan-induced GSH depletion and increased malondialdehyde level were significantly reversed by GCD (200 mg/kg) relative to gedunin and control. Nitrite levels was significantly reduced by GCD (200 mg/kg) and gedunin relative to control. The GCD (50 mg/kg) significantly reduced parasitemia (50.24%) and increased survival time compared to control. Gedunin-2-hydroxyropyl-β-cyclodextrin complex was more potent than gedunin in inhibiting inflammation and suppressing parasitemia in rodents.