Abstract:
In the form of a decoction, X. aethiopica is traditionally employed in the treatment of
bronchitis, asthma, arthritis and rheumatism in Ghana, Nigeria and Cameroon. This study
establishes the inhibitory effect of X. aethiopica and its principal constituent, xylopic acid, on
the arachidonic acid pathway of inflammation. Hydrogen sulphide is endogenously produced
in mammalian tissues from the enzymatic activity of cystathionine β-synthase and
cystathionine γ-lyase on L-cysteine. Its involvement in the local and systemic inflammatory
process has been documented in animal models. Recent studies have identified its activation
of phospholipase A2 as the mechanism involved in its anti-inflammatory role. We henceforth
conducted this study to investigate the inhibitory role of X. aethiopica and its principal
constituent xylopic acid on hydrogen sulphide-induced inflammation and eventual effect on
the activation of phospholipase A2. Sodium hydrogen sulphide (NaHS) was injected into the
mouse hind paw and oedema was monitored for 60 min. Paws were examined by the
histological method. X. aethiopica extract (30, 100, 300 mg kg-1) suppressed the mean
maximal swelling attained at 15 min to 42.58±1.66%, 42.58±1.66% and 34.91±2.39%,
respectively compared to the mean inflamed control response of 61.51±3.90%. The total paw
swellings induced over the 1 h were also significantly suppressed by 31.82±5.28%,
36.19±6.01%, and 31.65±5.16%, respectively. The xylopic acid (10, 30, 100 mg kg-1)
suppressed the mean maximal swelling attained at 15 min to 41.75±1.24%, 40.26±1.68% and
38.26±2.52%, respectively relative to the control response while the total paw swelling was
significantly suppressed by 34.08±4.49%, 38.19±4.50% and 43.40±5.09% respectively
relative to the inflamed control response. Histologically, there was a significant (P < 0.0001)
reduction in cytoplasmic vacuolation, inflammation, cellular degeneration, loss of tissue
organisation and necrotic tissues with administration of X. aethiopica extract and xylopic acid
in the inflamed paws of the mice. This study establishes that X. aethiopica extract, and
xylopic acid mediate their anti-inflammatory actions in part through inhibition of hydrogen
sulphide-induced inflammation and subsequently has an inhibitory role on phospholipase A2
activation.
