Abstract
The African wild olive (Olea europaea subsp. africana) is traditionally used as a hypotensive agent. Herb-drug interactions may result
from the concurrent use of herbal medicines and conventional prescription drugs. This
aspect was investigated by determining the effect of the extract on the in vitro intestinal epithelial permeation of selected hypotensive drugs using the Caco-2 cell
culture model. The phytochemical profiles of leaf extracts of African wild olive from
different localities in South Africa were compared, since efficacy is determined by
the chemical composition. Extracts were analysed using ultra-performance liquid chromatography.
The oleuropein concentration varied considerably from below the detection limit (4.94 µg/mL)
to 59.4 mg/g dry weight. Chemometric models constructed from the aligned chromatographic
data indicated only quantitative differences between the profiles. The leaf extract
was found to increase the permeability of propranolol in the absorptive direction
(Papp = 8.93 × 10−6 cm/s) across Caco-2 cell monolayers, but considerably decreased transport in the
secretory direction (Papp = 3.68 × 10−6 cm/s). The permeation of diltiazem was enhanced by the extract in both the absorptive
(Papp = 7.33 × 10−6 cm/s) as well as in the secretory direction (Papp = 7.16 × 10−6 cm/s), but a decrease in the efflux ratio was observed. The extract therefore caused
a net increase in the transport of both drugs in the absorptive direction due to an
inhibition effect on their efflux. This suggests a potential increase in the blood
levels of these drugs when taken simultaneously with African wild olive leaf extract,
indicating potential adverse effects that must be verified in vivo.
Key words
Olea europaea subspecies
africana
- Oleaceae - herb-drug interaction - oleuropein - antihypertensive drugs - Caco-2
cells
