Dodonaea viscosa Jacq. var. angustifolia (Sapindaceae) a medicinal plant used in folk medicine to treat diseases and inflammatory
conditions was investigated for its antioxidant and antibacterial properties because
it is the sole host plant for the edible stinkbug, Encosternum delegorguei Spinola, a traditional delicacy for the Vhavenda tribe of Limpopo Province of South
Africa. As insects are known to sequester compounds from their host plants [1], we
were interested to investigate the medicinal properties of D. viscosa and determine if the same compounds occur in the insect. D. viscosa methanol leaf extracts has antibacterial activity against several bacteria and viruses
[2]. Bioassay guided fractionation of dichloromethane and acetone fractions from serial
extraction of Dodonaea viscosa Jacq. var. angustifolia leaf powder yielded 3, 5, 7-trihydroxy-4′-methoxyflavone (kaempferide) (1); 5, 7, 4'-trihydroxy-3, 6-dimethoxyflavone (2); 5, 7-dihydroxy-3, 6, 4'-trimethoxyflavone (santin) (3); and 5-hydroxy -3, 7, 4'-trimethoxyflavone (4) and kaempferol (5). MIC of isolated compounds against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa varied from 16µg/ml to more than 250µg/ml. Good structure activity relationships
could be established. There were no ninhydrin positive compounds present in insect
extracts (i.e. peptides frequently responsible for antibacterial activities in many
insects probably absent). From bioautography of insect extracts zones of inhibition
coinciding with the Rf of some isolated compounds were found indicating that some of the compounds present
in D. viscosa could be present in the insect.
Acknowledgements: The NRF provided funding.
References: [1] Harborne, J.B., 1982. The Flavonoids: Advances in Research. In: T.J. Mabry (Ed.),
Chapman and Hall Ltd. Cambridge, UK. [2] Getie, M., et al. (2003) Fitoterapia 74:
139–143
