L Mambu

Activity of Ocimum basilicum, Ocimum canum, and Cymbopogon citratus essential oils against Plasmodium falciparum and mature-stage larvae of Anopheles funestus s.s.

The biological activities of essential oils from three plants grown in Cameroon: Ocimum basilicum, Ocimum canum, and Cymbopogon citratus were tested against Plasmodium falciparum and mature-stage larvae of Anopheles funestus. Gas chromatography and gas chromatography – mass spectrometry analyses showed that the main compounds are geranial, 1,8-cineole and linalool in C. citratus, O. canum and O. basilicum, respectively. Larvicidal tests carried out according to the protocol recommended by the World Health Organization showed that the essential oil of leaves of C. citratus is the most active against larvae of An. funestus (LC50 values = 35.5 ppm and 34.6 ppm, respectively, for larval stages III and IV after 6 h of exposure). Besides, the in vitro anti-plasmodial activity evaluated by the radioisotopic method showed that the C. citratus oil is the most active against P. falciparum, with an IC50 value of 4.2 ± 0.5 μg/mL compared with O. canum (20.6 ± 3.4 μg/mL) and O. basilicum (21 ± 4.6 μg/mL). These essential oils can be recommended for the development of natural biocides for fighting the larvae of malaria vectors and for the isolation of natural products with anti-malarial activity.

Uncommon chlorinated xanthone and other antibacterial compounds from the lichen Cladonia incrassata.

Bioassay-guided fractionation of an extract of the lichen Cladonia incrassata against Staphylococcus aureus led to a novel compound, 1,5-dihydroxy-2,4,6-trichloro-7-methylxanthone (1), along with six known compounds: (-)-usnic acid (2), didymic acid (3), condidymic acid (4), squamatic acid (5), thamnolic acid (6), and prasinic acid (7). Didymic, condidymic, and prasinic acids were isolated for the first time from C. incrassata. Didymic, condidymic, and (-)-usnic acids were active against S. aureus (a minimum inhibitory concentration of 7.5 µg/mL).

Cytochalasin E in the lichen Pleurosticta acetabulum. Anti-proliferative activity against human HT-29 colorectal cancer cells and quantitative variability

A biological screening of sixteen lichen extracts on human HT-29 colorectal cancer cells, led to the selection of Pleurosticta acetabulum, a lichen widely present in tree barks in Europe. Bioguided purification of the acetonic extract resulted in the isolation of cytochalasin E, a common fungal metabolite. This compound is responsible for the anti-proliferative activity of the extract. Its presence in lichens is reported here for the first time. LC-MS quantitation of cytochalasin E in different samples of P. acetabulum demonstrated quantitative variations of cytochalasin E production in the lichen and especially high concentrations in apothecia.

Fungal communities associated with Evernia prunastri, Ramalina fastigiata and Pleurosticta acetabulum: Three epiphytic lichens potentially active against Candida biofilms

Fungal communities associated to three epiphytic lichens active against Candida, were investigated using culture-based methods We hypothetized that associated fungi would contribute to lichens activities. The ability of specific fungi to grow inside or outside lichens was investigated. To detect biogenesis pathways involved in the production of secondary metabolites, genes coding for nonribosomal peptide synthetase (NRPS) and polyketide synthase I (PKS I) were screened by PCR from fungal DNA extracts. Both endo and epilichenic communities were isolated from two fructicose (Evernia prunastri and Ramalina fastigiata) and one foliose (Pleurosticta acetabulum) lichens. A total of 86 endolichenic and 114 epilichenic isolates were obtained, corresponding to 18 and 24 phylogenetic groups respectively suggesting a wide diversity of fungi. The communities and the species richness were distinct between the three lichens which hosted potentially new fungal species. Additionally, the endo- and epilichenic communities differed in their composition: Sordariomycetes were particularly abundant among endolichenic fungi and Dothideomycetes among epilichenic fungi. Only a few fungi colonized both habitats, such as S. fimicola, Cladosporium sp1 and Botrytis cinerea. Interestingly, Nemania serpens (with several genotypes) was the most abundant endolichenic fungus (53% of isolates) and was shared by the three lichens. Finally, 12 out of 36 phylogenetic groups revealed the presence of genes coding for nonribosomal peptide synthetase (NRPs) and polyketide synthase I (PKS I). This study shows that common lichens are reservoirs of diverse fungal communities, which could potentially contribute to global activity of the lichen and, therefore, deserve to be isolated for further chemical studies.