Olive tree extracts with potential leishmanicidal activity

Nowadays, drugs available for treating leishmaniasis are limited in number and all of them have different disadvantages such as toxicity, resistance and cost. Aiming to identify natural products with leishmanicidal activity, seven natural products derived from olive tree extracts were tested against three different Leishmania species: L. infantum MON-1, L. donovani MON-2 and L.major LV39, the former two causing visceral and the latter cutaneous leishmaniasis. The leishmanicidal activity was evaluated by a quantitative colorimetric assay using the oxidation-reduction Alamar Blue method on stationary or logarithmic phase promastigotes (Table 1).

Table 1: IC₅₀ (µg/ml)* of olive tree extractions against Leishmania promastigotes.

-: not determined; *IC50 of oleuropein and hydroxytyrosol is measured in µM; 1Olive Leaves Decoction; 2Olive Leaves Water Extraction; 3Olive Mill Waste Water extract
Olive tree extracts	L.infantum MON-1		L.donovani MON-2		L.major LV 39
	Stationary ph.	Logarithmic ph.	Stationary ph.	Logarithmic ph.	Stationary ph.	Logarithmic ph.
Oleuropein	>200	-	188	-	>200	-
Oleuropein mix 60%	>100	-	84	-	>100	-
Hydroxytyrosol	194	499	324	506	324	>649
OLD1	>100	-	52	-	-	-
OLWE2	>100	-	96	>100	-	-
OMWW3 XAD-4 (FCPC) OH-tyr:Tyr:Lactone 3:1:1	100	-	63	>100	100	-
OMWW XAD-4	-	-	>100	-	-	-

Hydroxytyrosol, oleuropein and some other olive tree extracts have a moderate antileishmanial activity against promastigotes and ongoing investigations concern their effect on intracellular amastigotes. Further more studies on these novel natural products obtained from the olive tree will include validation of their anti-leishmania activity in association with their effect on the immune system and antioxidant properties [1].

References: 1. Santangelo, C. et al (2007) Ann. Ist Super Sanita 43: 394–405.