Preliminary Study On The Acaricidal Ingredients From The Tenvermectin Producing Strain S. Avermitilis MHJ1011

Tenvermectins are a new kind of microorganism-derived sixteen-membered macrolactone antibiotics. Compared to avermectins, insecticidal test showed that tenvermectins possessed more efficient, low toxicity, broad spectrum and other advantages and it was considered to be a potential new generation of pesticides and veterinary drugs. This paper describes a preliminary study on the active ingredients of S. avermitilis MHJ1011. The contents of this paper includes the following three sections:, isolation and identification of metabolites from S. avermitilis MHJ1011, structural modification of tenvermectins and insecticidal tests of the obtained compounds.1. Fermentation was carried out in 50 L of fermentor(containing 30 L of production medium). By filtration, extraction, and concentration, The 260 g extract was obtained and 10 compounds were isolated with the help of silica gel, LH-20 and HPLC. The structures of the 10 compounds were elucidated on the basis of IR, UV and NMR spectroscopic analysis. Among of the 10 compounds, 3 compounds were known compounds including oligomycin A, oligomycin C, ivermectin B1 a and the other 7 compounds were new sixteen-membered macrolactone compounds. The 7 new compounds were assigned as 13α-hydroxy-4-ethy1 milbemycin β3(1), 13α-hydroxy-25-ethy1 milbemycin β3(2), 13α-hydroxy milbemycin β3(3), 13-oleandrose-25-isopropy1 milbemycin β3(4), 13-oleandrose-25-ethy1 milbemycin β3(5), 13-oleandrose milbemycin β3(6), 6β-hydroxy milbemycin β12(7).2. Tenvermectin A benzoate salt was synthesized by 5-steps(protected in C-5, oxidated in C-4", methylamino in C-4", to protect in C-5, and salt) from tenvermectin A, and acetamino tenvermectin A were synthesized by 5-steps(protected in C-5, oxidated in C-4", ammoniated in C-4", to protect in C-5, acetylation in C-4") from methylamino tenvermectin A.3. To clarify the insecticidal activity of compounds 1-7, methylamino tenvermectin benzoate(salt), acetylamino tenvermectin and tenvermectin against spider mites, the effects on the Tetranychus cinnabarinus were investigated under laboratory by leaf disc spray with a Potter spray tower. The LC50 values of the ten compounds against Tetranychus cinnabarinus were 0.0202, 0.1121, 0.1234, 0.0210, 0.0260, 0.0350, 0.0970, 0.0037, 0.0029 and 0.0045 mg/L respectively. The LC50 values of the ten compounds against Bursaphelenchus xylophilus were 4.1882, 10.9588, 11.4926, 4.2002, 4.3472, 4.5307, 9.6916, 1.7649, 1.0499 and 1.9344 mg/L, respectively.4. According to the relationship of insecticidal activity and structural differences, the results indicated that the longer C-25 side chains, the better of insecticidal activity. On the other hand, the compounds having oleandrosyl moiety at C-13 possessed better insecticidal activity than the compounds having a hydroxy group at C-13.This study showed that the tenvermectin producing strain have a lot of insecticidal and acaricidal secondary metabolites and is valuable for further exploration.