Purpose: To investigate the phytochemical constituents, acute toxicity and biological activities of
Lobelia herb (dried leaf of
Lobelia flaccida
; family: Campanulaceae), a popular medicinal agent used to
manage pain and epilepsy among other indications in Eastern Cape Region of South Africa.
Methods: Essential oil (EO) obtained from the dried leaf was analysed with gas chromatography-mas
spectroscopy GC/MS while an infusion extract of the herb was obtained by soaking in hot boiled water
(100
oC) for 24 h, filtered and the filtrate dried in vacuo. Phytochemical screening of the infusion extract
was performed to detect the presence of secondary plant metabolites and relative abundance of some
of the metabolites. The aqueous extract was evaluated for oral (p.o.) acute toxicity (LD
50) using the
Lorke’s method [30];, thereafter the extract was tested for anti-inflammatory activity on carrageenaninduced
rat paw oedema at 250 and 500 mg/kg, p.o., normal saline and aspirin (100 mg/kg, p.o.) used
as negative and positive controls respectively. Finally, the extract at 500 and 1000 mg/kg, p.o. was
tested for anticonvulsant activity on pentylene tetrazol (85 mg/kg, intraperitoneally)-induced convulsion
model in mice, normal saline and diazepam (1 mg/kg, i.p.) served as negative and positive control
groups respectively.
Results: EO yield was 0.022 % w/w and the two major compounds identified were acetophenone
(26.37 %) and caryophyllene (17.35 %). Phytochemical screening showed high concentration of
alkaloids, saponins and flavonoids among other constituents. LD
50 of the aqueous extract was ≥ 5000
mg/kg per oral while the aqueous extract exhibited significant (p < 0.01) anti-inflammatory activity on
carrageenan-induced rat paw oedema comparable to aspirin but insignificant anticonvulsant activity on
pentylene tetrazol-induced convulsion when compared with diazepam.
Conclusion: Lobelia herb is non-toxic, and possesses significant anti-inflammatory and mild
anticonvulsant activities. It is suggested that the essential oil of this herb should be screened for
pharmacological activities.
