Two clerodane diterpenes isolated from Polyalthia longifolia leaves: comparative structural features, anti-histaminic and anti-Helicobacter pylori activities

• Published in: Natural product research 2021-12, Vol.35 (23), p.5282-5286
• Main Authors: Edmond, Martina P., Mostafa, Nada M., El-Shazly, Mohamed, Singab, Abdel Nasser B.
• Format: Article
• Language: English
• Subjects: anti-helicobacter pylori; anti-histaminic; Antihistamines; Antiinfectives and antibacterials; Antimicrobial agents; Clarithromycin; clerodane; Decalin; Dichloromethane; Diclofenac; Diterpenes; Helicobacter pylori; Polyalthia longifolia
• ISSN: 1478-6419; 1478-6427
• DOI: 10.1080/14786419.2020.1753048

Phytochemical studies of methylene chloride soluble fraction from the 70% aqueous-alcoholic extract of Polyalthia longifolia (leaves) resulted in the isolation of two known clerodane diterpenes, namely: 16α-hydroxycleroda-3,13(14)-dien-16,15-olide (1) and (4→2)-abeo-16-hydroxy-cleroda-2,13(14)-dien-15,16-olide-3-al (2). The isolated compounds were evaluated for their anti-histaminic and anti-Helicobacter pylori activities. Compound 1 was more potent than 2 with IC 50 29.7 μg/mL and 189.2 μg/mL in the anti-histaminic assay and MIC equals to 31.25 μg/mL and 125 μg/mL in the anti-H. pylori assay, as compared with diclofenac (IC 50 = 17.9 μg/mL) and clarithromycin (MIC = 1.95 μg/mL), respectively. The differences in their structures, as well as their activity results, indicated important characteristic features necessary for activity. It was suggested that the decalin moiety in 1 was important for both activities. On the other hand, the (4→2)-abeo migration in 2 reduced both activities. The potent activities of 1 suggest its potential application as an anti-histaminic and antimicrobial agent.