Avermectins, New Family of Potent Anthelmintic Agents: Isolation and Chromatographic Properties

Abstract

The avermectins, a family of new anthelmintic agents, were isolated from the mycelia of Streptomyces avermitilis. Four closely related major components and four homologous minor components were separated from the complex. Solvent extraction, solvent partition, and adsorption methods were used to isolate and purify the complex; novel partition chromatography systems using Sephadex LH-20 were used to separate the components. A reverse-phase high-pressure liquid chromatography assay for the quantitative determination of all components was used extensively to monitor the purification methods.The avernectin complex, a family of new anthelmintic agents, is produced by fermentation of Streptomyces avermitilis (NRRL 8165), as described in a separate publication (1).The complex contains four closely related major components, Ala, A2a, Bia, and B2a, in varying proportions and four minor components, Alb, A2b, Blb, and B2b, each of which is a lower homolog ofthe corresponding major component. The structures and physicochemical properties of all components are the subject of a separate publication (G. Soc., in press).In this report, the isolation of the complex from broth, the separation of all of its components, and the chromatographic properties of each will be described. For the sake of simplicity, mixtures of homologs will be designated by omis- B2a, 6.74; A2b, 7.22; A2s, 8.00; B,I, 8.32; B,I., 9.70; Al,b, 11.06; and A,,, 11.78. The UV monitor was set at 246 nm to improve the resolution of a major impurity which exhibited a UV maximum at a lower wavelength. Although the UV maximum for avermectins occurred at 245 nm, sensitivity was only slightly reduced at 246 nm, whereas the sensitivity for the impurity was reduced substantially. The UV spectrum of B21 is given in Fig. 1 and is characteristic of all components. Recordings of high-pressure liquid chromatography (HPLC) assays of standard and unknown solutions are given in Fig. 2. RESULTSIsolation of avermectin complex. Approximately 8,000 liters of fermentation broth was filtered, and the cake was washed with water. The wet cake was then slurried in 3,000 liters of acetone, filtered, and washed with 400 liters of 80% acetone. The cake was discarded, and the combined extract and wash were concentrated to 800 liters. The concentrate was adjusted to pH 5 with dilute HCl and then extracted twice with 800-liter portions of methylene chloride.

Clinical Studies on the Efficacy of Different Topical Drugs with Ivermectin Injection in the Treatment of Egyptian Water Buffalo Calves Infested with Psoroptes Spp. Mites

“…The anthelmintic activity of the avermectins was first detected in 1979 (Miller et al, 1979). Ivermectin is a pioneering drug, a dihydro derivative of avermectin, originating from a microorganism isolated at Tokyo, Japan.…”

Effect of ivermectin on the life cycle and larval fat body of Culex quinquefasciatus

“…Ivermectin is a group of macrocyclical lactones, derived from 22,23-dihydro avermectin B1, with low water solubility that is produced by Streptomyces avermectilis (Burg, et al, 1979;Egerton et al, 1979;Miller et al, 1979;Chabala et al, 1980), being largely used as anti-parasitic in the domestic animals (Aziz et al, 1982;Campbell et al, 1983). Previous studies have shown that the avermectins are lethal for immature and adult stages of some insect orders (Strong and Brown, 1987) and efficient for the control of Culex quinquefasciatus (Freitas et al, 1996).…”

Ivermectin: enigmatic multifaceted ‘wonder’ drug continues to surprise and exceed expectations

“…The avermectin family displayed extraordinarily potent anthelmintic properties. [15][16][17] Ivermectin is a safer, more potent semisynthetic mixture of two chemically modified avermectins, comprising 80% of 22,23-dihydroavermectinB1a and 20% 22,23-dihydroavermectin-B1b (Figure 3). …”