Shi-Hong Luo

Schilancitrilactones A–C: Three Unique Nortriterpenoids from Schisandra lancifolia

Three unique nortriterpenoids, schilancitrilactones A-C (1-3), were isolated from the stems of Schisandra lancifolia . Compound 1 possesses a 5/5/7/5/5/5-fused hexacyclic ring system with a C(29) backbone, while 2 and 3 feature a C(27) skeleton with a 5/7/5/5/5-fused pentacyclic ring system. Their absolute stereochemistries were established by CD and single-crystal X-ray diffraction experiments. Compound 3 showed anti-HIV-1 activity with an EC(50) value of 27.54 μg/mL, and 1 exhibited antifeedant activity at 15.73 μg/cm(2).

Aphanamixoid A, a Potent Defensive Limonoid, with a New Carbon Skeleton from Aphanamixis polystachya

Aphanamixoid A (1), a limonoid with a new carbon skeleton, along with its biogenetically related limonoid aphanamixoid B (2), was isolated from the leaves and twigs of Aphanamixis polystachya . Their structures with the absolute stereochemistry were determined by spectroscopic analysis, X-ray crystallography and computational methods. The significant antifeedant activity of 1 against the generalist plant-feeding insect Helicoverpa armigera (EC50 = 0.015 μmol/cm(2)) suggested it may be a potent defensive component of A. polystachya.

Defensive Sesterterpenoids with Unusual Antipodal Cyclopentenones from the Leaves of Leucosceptrum canum

Two novel sesterterpenoids, leucosceptroids C (1) and D (2), possessing unusual antipodal cyclopentenones while maintaining the stereochemistry and functionality of the tricyclic cores, were discovered from the leaves of Leucosceptrum canum (Labiatae). Their structures including absolute stereochemistries were determined by comprehensive NMR, MS, and single-crystal X-ray diffraction analyses. The potent antifeedant activity of 1 against the generalist plant-feeding insect Helicoverpa armigera (EC(50) = 0.017 μmol/cm(2)) suggested them to be new defensive sesterterpenoids of L. canum.

Peltate glandular trichomes of Colquhounia coccinea var. mollis Harbor a new class of defensive sesterterpenoids

A new class of unique sesterterpenoids, colquhounoids A-C (1-3), were identified from the peltate glandular trichomes of Colquhounia coccinea var. mollis (Lamiaceae) through precise laser-microdissection coupled with UPLC/MS/MS and spectroscopic analyses and X-ray diffraction. Very interestingly, their structural features and defensive function are closely related to leucosceptroid-class sesterterpenoids harbored by the glandular trichomes of another Lamiaceae taxon, Leucosceptrum canum, even though this is morphologically distinct and taxonomically distant.

Novel polyesterified 3,4-seco-grayanane diterpenoids as antifeedants from Pieris formosa.

Pieris formosa is a poisonous plant to livestock and is used as an insecticide in rural areas of China. Two novel polyesterified 3,4-seco-grayanane diterpenoids, pierisoids A and B (1 and 2), were isolated from its flowers and were identified by spectroscopic analysis and X-ray diffraction. Both compounds showed obvious antifeedant activity against cotton bollworm, indicating their toxic properties, suggesting a defensive role of polyesterified 3,4-seco-grayanane diterpenoids for P. formosa against herbivores.

Defense sesterterpenoid lactones from Leucosceptrum canum

Ten sesterterpenoids, leucosceptroids E-N (1-10), possessing an α,β-unsaturated γ-lactone moiety, were isolated from the leaves and flowers of a woody Labiatae, Leucosceptrum canum. Their structures including relative stereochemistry were determined by comprehensive 1D and 2D NMR, MS, and in the case of 1 and 10, by single crystal X-ray diffraction analyses. This class of unique plant terpenoids was designated as leucosceptrane sesterterpenoids (=leucosceptroids). The potent antifeedant activity of the most abundant compound, leucosceptroid G (3), and a representative compound, leucosceptroid N (10), against the generalist plant-feeding insect Helicoverpa armigera suggested that they might also be defense compounds of L. canum against insects.

Phomopchalasins A and B, Two Cytochalasans with Polycyclic-Fused Skeletons from the Endophytic Fungus Phomopsis sp. shj2

Phomopchalasins A (1) and B (2), two novel cytochalasans with unprecedented carbon skeletons, and phomopchalasin C (3), containing a rare hydroperoxyl motif, were obtained from the endophytic fungus Phomopsis sp. shj2, which was first isolated from the Isodon eriocalyx var. laxiflora. Their structures were elucidated by extensive spectroscopic analyses, electronic circular dichroism (ECD) calculation, and X-ray crystallographic analysis. Notably, 1 possessed an unprecedented 5/6/5/8-fused tetracyclic ring system, and 2 featured a novel 5/6/6/7/5-fused pentacyclic skeleton. The cytotoxic, anti-inflammatory, and antimigratory activities of 1-3 were evaluated in vitro.

New Antifeedant C20 Terpenoids from Leucosceptrum canum

Three novel C(20) terpenoids, norleucosceptroids A-C (1-3), were isolated from the leaves and flowers of Leucosceptrum canum (Labiatae) and were identified by comprehensive spectroscopic analysis and, in the case of 1, single-crystal X-ray diffraction. Structurally, compounds 1-3 should be categorized as pentanor-sesterterpenoids rather than diterpenoids. Moderate antifeedant activity of 1-3 against the generalist plant-feeding insect Helicoverpa armigera was detected, suggesting that they might also be involved in the plant defense against insect herbivores.

Secondary Metabolites from Glycine soja and Their Growth Inhibitory Effect against Spodoptera litura

The wild soybean (Glycine soja Sieb. et Zucc) has been reported to be relatively resistant to insect and pathogenic pests. However, the responsible secondary metabolites in the aerial part of this important plant are largely unknown. From the aerial part of G. soja, 13 compounds were isolated and identified, including seven isoflavonoids (1-7), a cyclitol (8), two sterol derivatives (9 and 10), and three triterpenoids (11-13). Compound 7 is a new isoflavonoid, and compounds 9 and 10 are reported as natural products for the first time. The growth inhibitory activity of 1, 3, 4, and 8 against the larvae of Spodoptera litura was investigated. The most abundant isoflavonoid in the aerial part of G. soja, daidzein (1), which could not be metabolized by S. litura, was found to inhibit the insect larvae growth significantly in 3 days after feeding diets containing the compound. Compounds 3, 4, and 8, which could be partially or completely metabolized, were inactive. Our results suggested that the isoflavonoid daidzein (1) might function as a constitutive defense component in G. soja against insect pests.

o-Coumaric acid from invasive Eupatorium adenophorum is a potent phytotoxin

A phytochemical study of the invasive Eupatorium adenophorum indicated that the plant was rich in a phenolic compound o-coumaric acid (or 2-hydroxycoumaric acid). Biological investigations with the model plant Arabidopsis thaliana and crop plants showed that o-coumaric acid strongly inhibited seed germination, plant growth and root elongation, reduced the photosynthesis in old leaves, and induced the root cell death and the expression of genes related to senescence, oxidative stress, and systemic acquired resistance. The phytotoxic effects of o-coumaric acid exhibit selectivity between under- and above-ground parts of test plants and between E. adenophorum and other plants. These results indicate that o-coumaric acid is a potent toxin that might play an important role in the competition of E. adenophorum with its neighboring plants during its invasion and establishment.