Identification of chemical constituents of Zanthoxylum heitzii stem bark and their insecticidal activity against the malaria mosquito Anopheles gambiae

Abstract

BackgroundZanthoxylum heitzii bark extracts have insecticidal properties and have been reported to be used against malaria in Western Africa. Previously, it has been shown that a hexane extract of the bark is toxic to adult females of the mosquito Anopheles gambiae, a malaria vector. As part of our project on the control of malaria vectors using plant extracts, the phytochemistry of Z. heitzii bark hexane extract has been investigated with the aim to identify the major components with adulticidal and larvicidal effects on An. gambiae.MethodsZ. heitzii stem bark was extracted with hexane, and the extract was fractionated to isolate major components from the bark, identified by NMR spectroscopy. Isolated compounds were tested for toxicity towards adult female An. gambiae mosquitoes and for larvicidal effects towards An. gambiae.ResultsThe alkaloid dihydronitidine, the sesquiterpenoid caryophyllene oxide, the amide pellitorine and the lignan sesamin were identified as the major constituents in Z. heitzii bark. Pellitorine was toxic to both adult insects (LD50 50 ng/mg insect) and larvae (LD50 13 μg/ml). None of the other compounds were toxic to adults, but caryophyllene oxide and sesamin exhibited moderate larvicidal effects (LD50 > 150 μg/ml). A mixture of the four compounds in the same ratio as in the hexane extract showed higher toxicity (LD50 34 ng/mg insect) towards adult insects than the pure compounds.ConclusionThe toxicity of Z. heitzii bark hexane extract to An. gambiae is mostly due to pellitorine, although interactions between pellitorine and other, inactive constituents may enhance the activity of the extract.

Ovicidal and Larvicidal Activities of Ethanolic Leaf Extracts of Three Botanicals Against the Malaria Vector - Anopheles Gambiae

“…The Larvicidal efficacy of ethanol extracts of D. erecta, T. procumbens and P. purpureum against A. gambiae fourth instar larvae revealed that all the tested plant extracts were active against the test organism, as pupation was inhibited in a considerable number of larvae. Similar studies on the larvicidal activities of plants belonging to different families have been reported by various authors against the A. gambiae larvae including Gnetum ula, Spermacoce hispida [57], Artemisia annua [62], Plumbago zeylanica, Plumbago dawei and Plumbago stenophylla [66], Persea Americana [67], Citrus reticulata, Citrus limon, Citrus aurantifolia, Citrus sinensis, Citrus paradise [10], Clausena anisate [11], Zanthoxylum heitzii [12], Lippia adoensis [13], ISSN: 2456-7132 Available online at Journals.aijr.in…”

“…It has been discovered that plants generally produce many secondary metabolites which constitute an important source of microbicides, pesticides and many pharmaceutical drugs [9]. Varieties of plants such as Citrus paradise [10], Clausena anisate [11], Zanthoxylum heitzii [12], Lippia adoensis [13], Chromolaena odorata [14], Ageratum conyzoides [15] with insecticidal activities have been reported. Duranta erecta (Linn), also known as golden dewdrop, pigeon berry, angel whisper, or sky flower in English, is a shrub usually 1 to 3 m in height.…”

Natural products from Zanthoxylum heitzii with potent activity against the malaria parasite

“…The plant material was extracted and natural products isolated according to Moussavi et al [ 18 ] and Wangensteen et al [ 19 ]. Briefly, the stem bark, seeds and leaves were air dried and made into a powder (<1 mm).…”

“…The powdered plant materials were first extracted with hexane in a Soxhlet extractor until the effluent was colorless, and then subsequently extracted with ethyl acetate and ethanol in an accelerated solvent extractor, ASE350 (Dionex) [ 17 ]. The pure compounds were obtained from the bark hexane extract as previously described [ 18 , 19 ] by Si-gel normal phase and reverse phase C18 chromatography. The powdered bark (<1 mm), 10 g, was mixed with 100 g water and refluxed for 20 min to mimic a common way of preparing herbal drugs, making a decoction.…”

“…In this area, the bark is traditionally used to treat malaria [ 10 ]. Zanthoxylum heitzii bark extracts and major components of the extracts have previously been shown to have insecticidal activity [ 16 – 18 ] but it is unknown if Z. heitzii contains any compounds with significant anti-parasitic activity.…”