Traditional Kenyan herbal medicine: exploring natural products' therapeutics against schistosomiasis.

Praziquantel (PZQ) remains the only drug of choice for the treatment of schistosomiasis, caused by parasitic flatworms. The widespread use of PZQ in schistosomiasis endemic areas for about four decades raises concerns about the emergence of resistance of Schistosoma spp. to PZQ under drug selection pressure. This reinforces the urgency in finding alternative therapeutic options that could replace or complement PZQ. We explored the potential of medicinal plants commonly used by indigenes in Kenya for the treatment of various ailments including malaria, pneumonia, and diarrhoea for their antischistosomal properties. Employing the Soxhlet extraction method with different solvents, seven medicinal plants Artemisia annua, Ajuga remota, Bredilia micranta, Cordia africana, Physalis peruviana, Prunus africana and Senna didymobotrya were extracted. Qualitative phytochemical screening was performed to determine the presence of various phytochemicals in the plant extracts. Extracts were tested against Schistosoma mansoni newly transformed schistosomula (NTS) and adult worms and the schistosomicidal activity was determined by using the adenosine triphosphate quantitation assay. Phytochemical analysis of the extracts showed different classes of compounds such as alkaloids, tannins, terpenes, etc., in plant extracts active against S. mansoni worms. Seven extracts out of 22 resulted in <20% viability against NTS in 24 h at 100 µg/ml. Five of the extracts with inhibitory activity against NTS showed >69.7% and ≥72.4% reduction in viability against adult worms after exposure for 24 and 48 h, respectively. This study provides encouraging preliminary evidence that extracts of Kenyan medicinal plants deserve further study as potential alternative therapeutics that may form the basis for the development of the new treatments for schistosomiasis.

Constituents of the essential oil of Suregada zanzibariensis leaves are repellent to the mosquito, Anopheles gambiae s.s.

In traditional African communities, repellent volatiles from certain plants generated by direct burning or by thermal expulsion have played an important role in protecting households against vectors of malaria and other diseases. Previous research on volatile constituents of plants has shown that some are good sources of potent mosquito repellents. In this bioprospecting initiative, the essential oil of leaves of the tree, Suregada zanzibariensis Verdc. (Angiospermae: Euphobiaceae) was tested against the mosquito, Anopheles gambiae s.s. Giles (Diptera: Culicidae) and found to be repellent. Gas chromatography (GC), GC-linked mass spectrometry (GC-MS) and, where possible, GC-co-injections with authentic compounds, led to the identification of about 34 compounds in the essential oil. About 56% of the constituents were terpenoid ketones, mostly methyl ketones. Phenylacetaldehyde (14.4%), artemisia ketone (10.1%), (1S)-(-)-verbenone (12.1%) and geranyl acetone (9.4%) were the main constituents. Apart from phenylacetaldehyde, repellent activities of the other main constituents were higher than that of the essential oil. The blends of the main constituents in proportions found in the essential oil were more repellent to An. gambiae s.s. than was the parent oil (p < 0.05), and the presence of artemisia ketone in the blend caused a significant increase in the repellency of the resulting blend. These results suggested that blends of some terpenoid ketones can serve as effective An. gambiae s.s. mosquito repellents.

Repellent properties of delta-octalactone against the tsetse fly, Glossina morsitans morsitans.

Delta-octalactone, produced by several Bovidae, has been suggested as a potential repellant of tsetse fly attack. Racemic delta-octalactone was synthesized via an abbreviated route. The product was assayed against 3-day old starved teneral female tsetse flies, Glossina morsitans morsitans Wiedemann (Diptera: Glossinidae), in a choice wind tunnel and found to be a potent tsetse repellent at doses >or=0.05 mg in 200 microl of paraffin oil (0.05 >p >0.01).

C-methylated and C-prenylated isoflavonoids from root extract of Desmodium uncinatum.

A pterocarpan, 1,9-dihydroxy-3-methoxy-2-methylpterocarpan (named uncinacarpan) and two isoflavanones, 5,7-dihydroxy-2',3',4'-trimethoxy-6-(3-methylbut-2-enyl)isoflavanone (named uncinanone D) and 5,4'-dihydroxy-7,2'-dimethoxy-6-methylisoflavanone (named uncinanone E), were isolated from the CH(2)Cl(2) root extract of Desmodium uncinatum (Jacq.) DC and characterised by spectroscopic methods. In addition, a rare pterocarpan edudiol and two known abietane diterpenes, 7-oxo-15-hydroxydehydroabietic acid and 7-hydroxycallitrisic acid were identified. The fraction of the root extract that was analysed induced germination of Striga hermonthica seeds, but none of the isolated compounds showed this activity.

Development of a nutrient-dense complementary food using amaranth-sorghum grains.

Thin porridge from cereals and starchy tubers is a common complementary food in Sub Saharan Africa. It may be high in antinutrients, low in energy, and nutrient density hence inadequate in providing infants' high energy and nutrients requirements per unit body weight. Consequently, undernourishment levels among children under 5 years are high. Therefore, there is need to avail nutrient-dense complementary foods especially for children in low-resource settings. The study was aimed at developing a nutrient-dense complementary food from amaranth and sorghum grains. Amaranth grain, a pseudocereal, though rarely used as a complementary food in Kenya has a higher nutritional quality than other staples. Plant-based foods are known to have high levels of antinutrients. Steeping and germination were used to reduce the levels of antinutrients and enhance the bioavailability of minerals in the grains. Various steeped and germinated amaranth and sorghum grains formulations were made to find the ratio with the highest nutrient content and lowest antinutrient levels. The 90% amaranth-sorghum grains formulation had significantly (F = 32.133, P < 0.05) higher energy (5 kcal per g on dry weight basis) than the other formulations and a protein content of 14.4%. This is higher than the estimated protein needs from complementary foods even for a 12-23 months child of low breast milk intake (9.1 g/d). Antinutrients could not be detected which could imply enhanced nutrient bioavailability. Therefore, a nutrient-dense complementary food product was developed from steeped and germinated amaranth and sorghum grains with 90% amaranth grain. In ready to eat form, it would give an energy content of 1.7 kcal per g (dilution of 1:2 amaranth-sorghum flour to water) and 1.2 kcal per g (dilution of 1:4 amaranth-sorghum flour to water). It can be used as a nutrient-dense complementary food and for other vulnerable groups.

Responses of Glossina morsitans morsitans to blends of electroantennographically active compounds in the odors of its preferred (buffalo and ox) and nonpreferred (waterbuck) hosts.

In a previous study, comparison of the behavior of teneral Glossina morsitans morsitans on waterbuck, Kobus defassa (a refractory host), and on two preferred hosts, buffalo, Syncerus caffer, and ox, Bos indicus, suggested the presence of allomones in the waterbuck odor. Examination of the volatile odors by coupled gas chromatography-electroantennographic detection showed that the antennal receptors of the flies detected constituents common to the three bovids (phenols and aldehydes), as well as a series of compounds specific to waterbuck, including C8-C13 methyl ketones, delta-octalactone, and phenols. In this study, behavioral respones of teneral G. m. morsitans to different blends of these compounds were evaluated in a choice wind tunnel. The flies' responses to known or putative attractant blends (the latter comprising EAG-active constituents common to all three animals and those common to buffalo and ox, excluding the known tseste attractants, 4-methylphenol and 3-n-propylphenol), and to putative repellent (the blend of EAG-active compounds specific to the waterbuck volatiles), were different. A major difference related to their initial and final behaviors. When a choice of attractant blends (known or putative) and clean air was presented, flies initially responded by flying upwind toward the odor source, but later moved downwind and rested on either side of the tunnel, with some preference for the side with the odor treatments. However, when presented with a choice of waterbuck-specific blend (putative repellent) and clean air, the flies' initial reaction appeared random; flies flew upwind on either side, but eventually settled down on the odorless side of the tunnel. Flies that flew up the odor plume showed an aversion behavior to the blend. The results lend further support to previous indications for the existence of a tsetse repellent blend in waterbuck body odor and additional attractive constituents in buffalo and ox body odors.

Odor composition of preferred (buffalo and ox) and nonpreferred (waterbuck) hosts of some Savanna tsetse flies.

A previous study on the feeding responses of tsetse flies, Glossina morsitans morsitans, implicated the existence of allomonal barriers, both volatile and nonvolatile, on the nonpreferred host, waterbuck, Kobus defassa. In the present study, electroantennogram-active compounds in odors from waterbuck were compared with those of two preferred hosts of tsetse flies, buffalo, Syncerus caffer, and ox, Bos indicus. Odors from the three bovids were trapped on activated charcoal and/or reverse-phase (octadecyl bonded) silica and analyzed with a gas chromatography-linked electroantennographic detector (GC-EAD) and, where possible, identified by using gas chromatography-linked mass spectrometry (GC-MS) and chromatographic comparisons with authentic samples. The GC-EAD profiles (with G. m. morsitans antennae) of the odors of the two preferred hosts were comparable, comprising medium-chain, saturated or unsaturated aldehydes and phenols, with buffalo emitting a few more EAG-active aldehydes. Waterbuck odor gave a richer profile, consisting of fewer aldehydes but more phenolic components and a series of 2-ketones (C-C13) and delta-octalactone. This bovid also emits moderate amounts of C5-C9 straight-chain fatty acids, some of which were detected in buffalo and ox only in trace amounts. However, these did not elicit significant GC-EAD responses. Waterbuck profiles from the antennae of G. pallidipes showed broad similarity to those from G. m. morsitans, although the composition of aldehydes and ketones was somewhat different, indicating species-specific difference in the detection of host odors. Certain waterbuck-specific EAG-active components, particularly the 2-ketones and lactone, constitute a candidate allomonal blend in waterbuck odor.