Bioactive Diterpenes and Sesquiterpenes from the Rhizomes of Wild Ginger (Siphonochilus aethiopicus (Schweinf) B.L Burtt)
Wild ginger (Siphonochilus aethiopicus (Schweinf) B.L Burtt) is used in traditional medicines in the West and South of Africa. In the present study, the crude hexane extract of wild ginger was evaluated for in vitro bioactivity. The components isolated from the plant for the first time are: epi-curzerenone, furanodienone (sesquiterpenes), 8(17),12E-labdadiene-15,16-dial, 15-hydroxy-8(17),12E-labdadiene-16-al and 16-oxo-8(17),12E-labdadiene-15-oic acid (labdanes). Cytotoxicity determinations using five cell lines: SH-SY5Y (human, Caucasian, bone marrow, neuroblastoma), Jurkat (human, peripheral blood, leukaemia T cell), L929 (mouse, CH3/connective tissue, areolar and adipose tumour cells), Hep G2 (human, Caucasian, hepatocellular carcinoma) and Hs 27 (normal, human, foreskin cells) were carried out. Anti-trypanosomal activity against Trypanosoma brucei brucei (S427) blood stream forms and anti-bacterial activity against Mycobacterium aurum (CIP .104482) were also investigated. Activity against M. aurum was moderate and at 100μg/ml, the crude extract together with the labdanes showed specific cytotoxicity, indicating anti-cancer potency. Anti-trypanosomal activity was observed in the crude extract which increased with the pure components: 8(17),12E-labdadiene-15,16-dial (MIC = 5.3 μM) and the sesquiterpenoids (MIC = 6.9 μM) as compared to suramin activity (MIC = 10 μM). This anti-trypanosomal activity which is being reported for the first time indicates possible usage against sleeping sickness and nagana in cattle.
Key words: Anti-bacterial activity; Anti-trypanosomal activity; Cytotoxicity; Labdane diterpenoids; Sesquiterpenoids; Siphonochilus aethiopicus.