Xylogranatins F–R: Antifeedants from the Chinese Mangrove, Xylocarpus granatum, A New Biogenetic Pathway to Tetranortriterpenoids

Abstract

Thirteen limonoids with a new carbon skeleton, the xylogranatins F-R (1-13), have been isolated from the seeds of a Chinese mangrove, Xylocarpus granatum; two recently reported compounds, xylogranatins C and D were also isolated. Their structures were elucidated on the basis of spectroscopic data and chemical methods. The absolute configurations of these compounds were determined by using the modified Mosher MTPA ester method and by quantum chemical circular dichroism (CD) calculations. Xylogranatins F-Q are the first aromatic B-ring limonoids found in nature. They belong to two substructural classes, of which one (1-3) contains a pyridine ring while the other one (4-12) contains a central furan core. Xylogranatins C and R can be considered to be key biosynthetic intermediates, while xylogranatin D, the only limonoid found so far with a carbon skeleton that conatains a C(30)-C(9) linkage, is apparently an artifact. The structures of these compounds suggest a new biogenetic pathway to tetranortriterpenoids. Xylogranatins F, G and R were found to exhibit marked antifeedant activity against the third instar larvae of Mythimna separata (Walker) at a concentration of 1 mg mL(-1). The most potent compound tested was xylogranatin G. Its AFC(50) (concentration for 50 % antifeedant activity) values at the exposure times of 24 and 48 h were 0.31 and 0.30 mg mL(-1), respectively.

The Assignment of Absolute Stereostructures through Quantum Chemical Circular Dichroism Calculations

“…[80] As can be seen in Figure 8, the theoretical simulation of the region Figure 8. Assignment of the absolute axial configuration of xylogranatine F (6) by TDDFT and DFT/MRCI calculations.…”

Recent progress in the chemistry and biology of limonoids

“…4 Limonoids exhibited a wide spectrum of biological properties including cytotoxic, [5][6][7][8] antioxidant, 9,10 antiinammatory, 11,12 neuroprotective, 13,14 antiviral, 15 antimicrobial, 16,17 antiprotozoal, 18 antimalarial, [19][20][21] insect antifeedant, [22][23][24][25][26] and insecticidal activities. [27][28][29] The present review highlights the advances of limonoids in regard to isolation, total synthesis, and structural modications with the relevant biological properties.…”

Limonoids and Tirucallane Derivatives from the Seeds of a Krishna Mangrove, Xylocarpus moluccensis

“…[10][11][12] To date, 42 mexicanolides and 23 phragmalins, including three 1,8,9-phragmalin ortho esters, eight 8,9,30-phragmalin ortho esters, and 12 polyhydroxylated phragmalins, have been isolated from the wood, seeds, and fruits of X. granatum and X. moluccensis. 13 We recently identified seven phragmalins, moluccensins A-G, 14 from seeds of an Indian mangrove, X. moluccensis, collected in the mangrove wetlands of Krishna estuary, Andhra…”