Ali M Syed, Ravikumar S, Beula J Margaret, Anuradha V, Yogananth N
School of Marine Sciences, Department of Oceanography and CAS, Alagappa University, Thondi, India.
J Vector Borne Dis. 2014 Jun;51(2):106-14.
BACKGROUND & OBJECTIVES: Mosquito control is facing a threat due to the emergence of resistance to synthetic insecticides. Insecticides of botanical origin could serve as potential alternatives in future. Larvicidal efficacies of different parts of mangrove plants belonging to Rhizophoraceae family were tested against the late IV instar larvae of dengue vector, Aedes aegypti.
Different plant parts (leaf, bark, root, stilt root, hypocotyl and flower) of Rhizophoraceae family mangrove plants (Bruguiera cylindrica, Ceriops decandra, Rhizophora mucronata and R. apiculata) were collected from Karangadu southeast coast of India. The larval mortality was observed after 24 h exposure. Repellency bioassays were carried out in a 10 Χ 10 Χ 3 m room at 27- 35°C and 60- 80% RH. The bark (A3 and E1) and stilt root (A3 and E4) fractions of R. mucronata with different concentrations (0.25, 0.50, 0.75, 1, 2 and 4 mg/cm) were applied on one arm.
The stilt root crude extract of R. mucronata showed maximum larvicidal activity (LC50 value 0.0275 ± 0.0066 μg/ml and LC90 = 0.0695 ± 0.156 μg/ml) followed by the bark extract (LC50 value of 0.03 ± 0.0076 μg/ml and LC90 = 0.0915 ± 0.156 μg/ml). Column chromatographic fractions of R. mucronata bark extracts (E1) showed maximum larvicidal activity (LC50 = 0.0496 ± 0.0085 μg/ml and LC90 = 0.1264 ± 0.052 μg/ml) followed by the acetone extract (LC50 = 0.0564 ± 0.0069 μg/ml and LC90 = 0.1187 ± 0.05 μg/ml). Ethanolic fraction (E4) of R. mucronata stilt root extracts showed maximum larvicidal activity (LC50 = 0.0484 ± 0.0078 μg/ml and LC90 = 0.1191 ± 0.025 μg/ml) followed by acetone fraction (A3) (LC50 = 0.0419 ± 0.0059 μg/ml and LC90 = 0.0955 ± 0.069 μg/ml). Repellent activity of R. mucronata stilt root and bark extracts (A3) showed maximum percentage of protection (97.5%) with 9.1 h protection time at 4 mg concentration of the stilt root extract. Moreover, ethanolic fraction of the stilt root (E4) extract showed maximum percentage of protection (100%) with 10 h protection time at 4 mg concentration. GC-MS analysis revealed that R. mucronata possesses variety of biopesticidal compounds.
INTERPRETATION & CONCLUSION: The results as well as the significance of this preliminary investigation highlight the importance of R. mucronata as a novel source for natural insecticidal products.
由于对合成杀虫剂产生抗性，蚊虫控制正面临威胁。植物源杀虫剂未来可能成为潜在的替代品。测试了红树科不同植物部位对登革热媒介埃及伊蚊IV龄晚期幼虫的杀幼虫效果。
从印度东南海岸的卡兰加杜采集了红树科红树植物（柱果木榄、红海榄、红树和尖叶红树）的不同植物部位（叶、树皮、根、支柱根、下胚轴和花）。暴露24小时后观察幼虫死亡率。在温度为27 - 35°C、相对湿度为60 - 80%的10×10×3米房间内进行驱避生物测定。将不同浓度（0.25、0.50、0.75、1、2和4毫克/平方厘米）的红树树皮（A3和E1）和支柱根（A3和E4）提取物涂在一只手臂上。
红树支柱根粗提物显示出最大的杀幼虫活性（LC50值为0.0275±0.0066微克/毫升，LC90 = 0.0695±0.156微克/毫升），其次是树皮提取物（LC50值为0.03±0.0076微克/毫升，LC90 = 0.0915±0.156微克/毫升）。红树树皮提取物（E1）的柱色谱馏分显示出最大的杀幼虫活性（LC50 = 0.0496±0.0085微克/毫升，LC90 = 0.1264±0.052微克/毫升），其次是丙酮提取物（LC50 = 0.0564±0.0069微克/毫升，LC90 = 0.1187±0.05微克/毫升）。红树支柱根提取物的乙醇馏分（E4）显示出最大的杀幼虫活性（LC50 = 0.0484±0.0078微克/毫升，LC90 = 0.1191±0.025微克/毫升），其次是丙酮馏分（A3）（LC50 = 0.0419±0.0059微克/毫升，LC90 = 0.0955±0.069微克/毫升）。红树支柱根和树皮提取物（A3）的驱避活性在支柱根提取物浓度为4毫克时显示出最大保护率（97.5%），保护时间为9.1小时。此外，支柱根提取物（E4）的乙醇馏分在浓度为4毫克时显示出最大保护率（100%），保护时间为10小时。气相色谱 - 质谱分析表明红树含有多种生物杀虫化合物。
该初步研究的结果及其意义突出了红树作为天然杀虫产品新来源的重要性。
