The discovery of bioactive natural products is a basis for development of novel
pharmaceuticals. Indigenous medicinal plants which are largely unexplored offer
chemical diversity with structural complexity and biological potency. Despite their
ethnomedicinal usage, there is little information on the bioactive components of Dioclea
reflexa and Cussonia arborea. This study was designed to isolate and characterise the
secondary metabolites from the roots of D. reflexa and C. arborea, and evaluate free
radical scavenging activity of the isolates.
One kilogramme each of authenticated D. reflexa root and C. arborea root-bark were
collected from Eruwa, Oyo State. The air-dried samples of D. reflexa and C. arborea
were purposively extracted with ethanol and methanol respectively. The crude extracts
were separately fractionated on silica gel column chromatography with gradient elution
using various solvents. The sub-fractions were further subjected to a combination of
chromatographic techniques for isolation of pure compounds. Structures of isolated
compounds were elucidated using one and two-dimensional Nuclear Magnetic
Resonance (NMR), Infrared (IR), Ultra-Violet-Visible and Mass Spectroscopy (MS)
techniques, and comparison with literature data for known compounds. The isolated
compounds were evaluated for free radical scavenging potential in comparison with
butylated hydroxyanisole following standard method.
The ethanol extract (85 g) of D. reflexa on column chromatography gave β-sitosterol 1,
lupeol 2, aurantiamide acetate 3, mearnsetin 6, 7,4′-dihydroxyflavone 7 and 3,5-
dihydoxy-4-methoxybenzoic acid 8. The column yielded two new compounds, named
lexaflavanone 4 and reflevone 5. Lexaflavanone showed the presence of sixteen
carbons: 8C, 1CH2, 6CH and 1CH3. The MS gave M+
peak at m/z 302.0769 (Calcd.
302.0792), with 10 degree of unsaturation, corresponding to C16H14O6. The NMR
signals were seen at δ 8.53, 7.70 (1H, d, J= 8.5 Hz), 6.58 (2H, s), 6.55 (1H, dd, J= 2,
8.5 Hz), 6.42 (1H, d, J= 2Hz), 5.36 (1H, dd, J= 2.5, 12.5 Hz), 2.93 (1H, dd, J= 12.5, 17
Hz, H-3axial) and 2.66 (1H, dd, J= 3, 17 Hz, H-3equi). The IR absorptions (υmax, cm-1
OH (3361) C=O (1652) and C-C in ring (2917) were also detected. Reflevone,
molecular formula C16H12O6 suggested δH signals: 6.54 (1H, s), 6.97(1H, dd), 7.02(1H,
d) and 7.06 (2H, s), and δC signal: 177.9 (C=O) typical of flavone. In addition, its infrared stretching absorptions (υmax, cm-1
) revealed C-H sp2
(1570) and O-H (3377). The characteristics peaks of retro-Diels-Alder cleavage of ring C were observed in MS
spectrum at m/z 137 and 166. Column chromatography of the methanol extract (18 g) of
C. arborea yielded three known compounds, stigmasterol 9, oleanolic acid 10 and
hederagenin 11 when compared with literature. The compounds were however new to
the species of C. arborea. Lexaflavanone, reflevone and hederagenin exhibited free
radical scavenging activity with IC50 of 58.14, 322.0 and 105.0 μM respectively.
The plants have potentials for the development of drugs for the treatment of diseases
with oxidative stress due to their free radical scavenging activities. Lexaflavanone and
reflevone obtained from D. reflexa are new additions to the library of chemical
CDR, C (2021). Isolation And Characterisation Of Secondary Metabolites From Dioclea Reflexa (Hook F.) And Cussonia Arborea (Hochst). Afribary.com: Retrieved April 17, 2021, from https://afribary.com/works/isolation-and-characterisation-of-secondary-metabolites-from-dioclea-reflexa-hook-f-and-cussonia-arborea-hochst
Coalition, CDR. "Isolation And Characterisation Of Secondary Metabolites From Dioclea Reflexa (Hook F.) And Cussonia Arborea (Hochst)" Afribary.com. Afribary.com, 03 Apr. 2021, https://afribary.com/works/isolation-and-characterisation-of-secondary-metabolites-from-dioclea-reflexa-hook-f-and-cussonia-arborea-hochst . Accessed 17 Apr. 2021.
Coalition, CDR. "Isolation And Characterisation Of Secondary Metabolites From Dioclea Reflexa (Hook F.) And Cussonia Arborea (Hochst)". Afribary.com, Afribary.com, 03 Apr. 2021. Web. 17 Apr. 2021. < https://afribary.com/works/isolation-and-characterisation-of-secondary-metabolites-from-dioclea-reflexa-hook-f-and-cussonia-arborea-hochst >.
Coalition, CDR. "Isolation And Characterisation Of Secondary Metabolites From Dioclea Reflexa (Hook F.) And Cussonia Arborea (Hochst)" Afribary.com (2021). Accessed April 17, 2021. https://afribary.com/works/isolation-and-characterisation-of-secondary-metabolites-from-dioclea-reflexa-hook-f-and-cussonia-arborea-hochst