Quassinoids from Picrasma chinensis with Insecticidal Activity against Adults and Larvae of Diaphorina citri Kuwayama and Neuroprotective Effect

Abstract

Eleven new tetracyclic quassinoids, picrachinensin A−K (1−11), along with six known congeners, were isolated from the stems and leaves of Picrasma chinensis. Their structures were elucidated by integrated multiple spectroscopic techniques, singlecrystal X-ray diffraction analysis, and electronic circular dichroism. Notably, compounds 3 and 4 are a pair of undescribed epimers, and 8 and 9 are unusual quassinoids with a hydroxymethyl group at C-13. Biologically, compound 7 exhibited insecticidal activity on both adults and larvae of Diaphorina citri Kuwayama even more effectively than the positive control (abamectin), with an LD 50 of 55.69 mg/L for adults and a corrected mortality rate of 30.42 ± 2.78% for larvae (100 mg/L). According to preliminary structure− activity relationship investigations, the hydroxymethyl at the C-13 position of quassinoids was beneficial for their insecticidal activity. In addition, compounds 1, 4, and 12 exhibited excellent neuroprotective effect against H 2 O 2 -induced oxidative injury on SH-SY5Y cells, with more potent activity than the positive control (Trolox), and all the compounds exhibited no cytotoxicity to SH-SY5Y and BV-2 cells at the indicated concentrations.

Quassinoids from Twigs of Harrisonia perforata (Blanco) Merr and Their Anti-Parkinson’s Disease Effect

“…The remaining part of the structure and the relative configuration of perforalactone K (6) was similar to that of perforalactone J (5) S37). Except for three carbonyls and two trisubstituted double bonds, the remaining four degrees of unsaturation indicated the presence of a four-ring system in perforalactone L (7). All the data suggested that perforalactone L ( 7) is a C-19 quassinoid.…”

“…The 1 H NMR spectrum displayed signals due to two olefinic protons [δH 5.88 (1H, dd, J = 3.0,1.5 Hz); δH 5.76 (1H, d, J = 1.5 Hz)] and four tertiary methyls [δH 1.16 (3H, s), 1.31 (3H, s), and 1.94 (3H, s), and 2.19 (3H, s)] (Table 2, Figure S37). Except for three carbonyls and two trisubstituted double bonds, the remaining four degrees of unsaturation indicated the presence of a four-ring system in perforalactone L (7). All the data suggested that perforalactone L ( 7) is a C-19 quassinoid.…”

“…Although their biogenetic pathway is not yet fully understood, it is believed that they originate from tetracyclic tirucallane triterpene and undergo a series of oxidation, rearrangement, and recyclization steps [3]. Additionally, these quassinoids have been found to exhibit a wide range of biological and pharmacological effects, including antiinflammatory, anti-tumor, and anti-malarial properties [1,[3][4][5][6][7]. Therefore, this type of compounds has become an area of significant interest in the scientific community [8,9].…”

“…For example, harpertrioate A reduced Aβ42 and Aβ40 production and shifted APP processing toward a nonamyloidogenic pathway, while perforalactones D and E significantly induced lysosomal biogenesis through transcriptional activation of lysosomal genes [6,22]. As part of our ongoing work to discover [23] bioactive molecules from plant [14,20,21,[24][25][26][27], we isolated seven undescribed quassinoids (1)(2)(3)(4)(5)(6)(7), including six C-20 and one C-19 quassinoids from the twigs of this plant. We also verified the oxidative degradation of C-25 quassinoid, perforalactone B (Figure 1), to the C-20 quassinoid, perforaquassin A, through chemical transformation, and then the crucial "link" between C-25 type and C-20 type quassinoids was proposed.…”