[Establishment of a quantitative method for GC analysis of polyoxyethylene (35) castor oil in microemulsion extracts].

With the continuous exploration of microemulsions as solvents for traditional Chinese medicine extraction, polyoxyethy-lene(35) castor oil(CrEL), a commonly used surfactant, is being utilized by researchers. However, the problem of detecting residues of this surfactant in microemulsion extracts has greatly hampered the further development of microemulsion solvents. Based on the chemical structures of the components in CrEL and the content determination method of castor oil in the 2020 edition of the Chinese Pharmacopoeia(Vol. Ⅳ), this study employed gas chromatography(GC) and single-factor experiments to optimize the preparation method of methyl ricinoleate from CrEL. The conversion coefficient between the two was validated, and the optimal sample preparation method was used to process microemulsion extracts of Zexie Decoction from three batches. The content of methyl ricinoleate generated was determined, and the content of CrEL in the microemulsion extracts of Zexie Decoction was calculated using the above conversion coefficient. The results showed that the optimal preparation method for CrEL was determined. Specifically, 10 mL of 1 mol·L~(-1) KOH-methanol solution was heated at 60 ℃ for 15 min in a water bath. Subsequently, 10 mL of boron trifluoride etherate-methanol(1∶3) solution was heated at 60 ℃ for 15 min in a water bath, followed by extraction with n-hexane twice. CrEL could stably produce 20.84% methyl ricinoleate. According to this conversion coefficient, the average mass concentration of CrEL in the three batches of Zexie Decoction microemulsion extracts was 11.94 mg·mL~(-1), which was not significantly different from the CrEL mass concentration of 11.57 mg·mL~(-1) during microemulsion formulation, indicating that the established content determination method of this study was highly accurate, sensitive, and repeatable. It can be used for subsequent research on microemulsion extracts of Zexie Decoction and provide a reference for quality control of other drug formulations containing CrEL.

Identification of an antifungal metabolite produced by a potential biocontrol Actinomyces strain A01 / Identificação de um metabólito antifúngico produzido pela cepa Actinomyces A01

Actinomyces strain A01 was isolated from soil of a vegetable field in the suburb of Beijing, China. According to the morphological, cultural, physiological and biochemical characteristics, and 16S rDNA sequence analysis, strain A01 was identified as Streptomyces lydicus. In the antimicrobial spectrum test strain A01 presented a stable and strong inhibitory activity against several plant pathogenic fungi such as Fusarium oxysporum, Botrytis cinerea, Monilinia laxa, etc. However, no antibacterial activity was found. In pot experiments in greenhouse, the development of tomato gray mold was markedly suppressed by treatment with the fermentation broth of the strain A01, and the control efficacy was higher than those of Pyrimethanil and Polyoxin. A main antifungal compound (purity 99.503 percent) was obtained from the fermentation broth of strain A01 using column chromatography and HPLC. The chemical structural analysis with UV, IR, MS, and NMR confirmed that the compound produced by the strain A01 is natamycin, a polyene antibiotic produced by S. chattanovgensis, S. natalensis, and S. gilvosporeus, widely used as a natural biological preservative for food according to previous reports. The present study revealed a new producing strain of natamycin and its potential application as a biological control agent for fungal plant diseases.

A cepa Actinomyces A01 foi isolada do solo de um campo agrícola no subúrbio de Beijing, China. De acordo com as características morfológicas, culturais, fisiológicas e bioquímicas, e análise da sequência 16S rDNA , a cepa A01 foi identificada como Streptomyces lydicus. Nos testes de espectro antimicrobiano, a cepa A01 apresentou atividade inibitória intensa e estável contra vários fungos patogênicos para plantas, como Fusarium oxysporum, Botrytis cinerea, Monilia laxa, etc. Entretanto, não foi encontrada atividade antibacteriana. Em experimentos em estufas, o desenvolvimento do fungo cinza do tomate foi fortemente inibido pelo tratamento com o caldo de fermentação da cepa A01, com eficiência superior à do pyremethanil e polyoxin. Por cromatografia em coluna e HPLC, obteve-se um composto fúngico (pureza 99,503 por cento), cuja análise estrutural por UV, IR, MS e NMR revelou ser natamicina, um antibiótico polienico produzido por S. chattanovgensis, S. natalensis e S.gilvosporeus, empregado como conservador biológico natural em alimentos. O presente estudo relata a detecção de uma nova cepa produtora de natamicina e sua aplicação potencial como um agente de controle biológico de doenças fúngicas em plantas.