Abstract
Chemical investigations on the fermentation extract obtained from an ascidian-derived Streptomyces sp. (USC-16018) yielded a new ansamycin polyketide, herbimycin G (1), as well as a known macrocyclic polyketide, elaiophylin (2), and four known diketopiperazines (3–6). The structures of the compounds were elucidated based on 1D/2D NMR and MS data. The absolute configuration of 1 was established by comparison of experimental and predicted electronic circular dichroism (ECD) data. Antiplasmodial activities were tested for the natural products against chloroquine sensitive (3D7) and chloroquine resistant (Dd2) Plasmodium falciparum strains; the two polyketides (1–2) demonstrated an inhibition of >75% against both parasite strains and while 2 was highly cytotoxic, herbimycin G (1) showed no cytotoxicity and good predicted water solubility.
Highlights
Malaria is a vector-borne disease caused by protozoan parasites of the genus Plasmodium, which results in more than 400,000 deaths annually [1]
The configuration of the macrolactam ring is consistent with herbimycin analogues previously reported in the literature, but herbimycin G (1) is the first example of an ansamycin compound that reported in the literature, but herbimycin G (1) is the first example of an ansamycin compound contains a 2,6-disubstituted 4-hydroxyl-cyclohexenone ring
These results showed that marine actinomycetes were a valuable source for the discovery of new new secondary metabolites
Summary
Malaria is a vector-borne disease caused by protozoan parasites of the genus Plasmodium, which results in more than 400,000 deaths annually [1]. The sporozoites are carried to the liver, where they reproduce asexually to give rise to thousands of merozoites that spread through the body via the bloodstream [2,3] During this intraerythrocytic cycle, the clinical manifestations of the disease appear, and the human host experiences strong fevers and chills [3,4]. Within the gut of the mosquito, they undergo gametogenesis and fertilization, develop into oocysts, which asexually produce new sporozoites. These migrate to the mosquito’s salivary glands and the life cycle of the parasite begins again once the mosquito feeds on a new human. Plastid in the Plasmodium parasite andparasite inhibiting protein synthesis in this organelle ansamycin.
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