Abstract
A new lignan (T4) and three known lignans (T1, T2, and T3) were isolated from the methanol extract of the roots of Phryma leptostachya using bioassay-guided method, and their structures were identified as phrymarolin I (T1), II (T2), haedoxan A (T3), and methyl 4-((6a-acetoxy-4-(6-methoxybenzo[d][1,3]dioxol-5-yl)tetrahydro-1H,3H-furo[3,4–c]furan-1-yl)oxy)-1-hydroxy-2,2-dimethoxy-5-oxocyclopent-3-ene-1-carboxylate (T4) byNMR and ESI-MS spectral data. Bioassay results revealed that haedoxan A exhibited remarkably high insecticidal activity against Mythimna separata with a stomach toxicity LC50 value of 17.06 mg/L and a topical toxicity LC50 value of 1123.14 mg/L at 24 h, respectively. Phrymarolin I and compound T4 also showed some stomach toxicity against M. separata with KD50 values of 3450.21 mg/L at 4 h and 2807.10 mg/L at 8 h, respectively. In addition, phrymarolin I and haedoxan A exhibited some stomach toxicity against Plutella xylostella with an LC50 value of 1432.05 and 857.28 mg/L at 48 h, respectively. In conclusion, this study demonstrated that lignans from P. leptostachya are promising as a novel class of insecticides or insecticide lead compounds for developing botanical pesticides.
Highlights
Phryma leptostachya is a perennial herb and is widely found in the Himalayas, temperate Asia, and northern East America [1,2,3]
P. leptostachya has been traditionally used as a natural botanical insecticide in East Asia [5,6,7,8]
We isolated a new lignan (T4) and three known lignans from the roots of P. leptostachya, and we demonstrated that haedoxan A exhibited remarkably high insecticidal activity against M. separata with a stomach toxicity LC50 value of
Summary
Phryma leptostachya is a perennial herb and is widely found in the Himalayas, temperate Asia, and northern East America [1,2,3]. The plant is a traditional Chinese medicine (TCM), which is commonly used to treat inflammatory diseases, such as allergic dermatitis, gout, and itch [4]. P. leptostachya has been traditionally used as a natural botanical insecticide in East Asia [5,6,7,8]. Previous phytochemical investigations showed that this plant is rich in lignans, many of which have a unique oxygenated 3,7-dioxabicyclo[3.3.0]octane skeleton, such as phrymarolin I, II, and haedoxan. A [1,10,11,12] These lignans are considered as the main insecticidal active ingredients in
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