Pathogenic plant oomycetes cause devastating damage to fruits and vegetables worldwide. Plant essential oils (EOs) are known to be promising candidates for the development of fungicides. In this study, we isolated twelve EOs from Tetradium ruticarpum, Tetradium daniellii, Tetradium fraxinifolium, Zanthoxylum armatum, Ruta graveolens, and Citrus medica leaves and fruits. We then investigated their chemical composition and antifungal activity against phytopathogenic oomycetes. Our results demonstrated that Z. armatum fruit essential oil (ZFO) in particular substantially inhibited the mycelial growth of Phytophthora capsici. Similarly, ZFO also strongly suppressed spore production and germination of P. capsici, and the application of ZFO significantly reduced disease symptoms caused by P. capsici in pepper. Furthermore, results from microscopic and biochemical studies indicated that ZFO damaged the ultrastructure and destroyed the membrane integrity of P. capsici, leading to the leakage of the cellular contents and ultimately causing cell death. It was concluded that ZFO could enhance the activities of defense-related enzymes in pepper fruits, which may also be responsible for the inhibition of phytophthora disease. Moreover, linalool and D-limonene were proven to be the primary effective components of ZFO. Our results collectively indicate that ZFO could be a potential candidate for the management of disease caused by P. capsici.

Tetradium ruticarpum (Juss.) Benth. belong to the family of Rutaceae. The complete and nearly ripe fruits of T. ruticarpum is used as traditional Chinese medicine and phytochemical investigations have been conducted on extracts of the seeds of T. ruticarpum to provide scientific validation of its properties. In this study, we successfully isolated two new quinolone alkaloids (1-2) from the MeOH extractive of nearly ripe fruits of T. ruticarpum. The structure elucidation of these compounds was determined by one- and two-dimensional nuclear magnetic resonance, ultraviolet and electrospray ionisation time-of-flight mass spectrometry. This finding expands the understanding of the natural constituents of the Rutaceae, in particular, the Tetradium genera.

A new nortriterpene saponin, 3-O-β-d-glucuronopyranosyl-30-norolean-12,20(29)-dien-23- oxo-28-oic acid, namely bigelovii D (11), was isolated from the hydroalcoholic extract of herbs of Salicornia bigelovii along with 10 known saponins (1–10). Their chemical structures were identified on the basis of spectroscopic analyses including two-dimensional NMR and a comparison with literature data. Some of these compounds showed potent antifungal activities in vitro. Compounds 3, 4, 5, 6, 7, 10 and 11 demonstrated potent inhibitory activities against Colletotrichum gloeosporioides and compound 11 displayed broad-spectrum inhibitory activity against Alternaria alternata, A. solani, Botrytis cinerea, C. gloeosporioides, Fusarium graminearum, F. verticilloides, Thanatephorus cucumeris and Sclerotinia sclerotiorum, with EC₅₀ values ranging from 13.6 to 36.3 μg/mL.

A rare new quinolone alkaloid containing three degrees of unsaturation in the side chain, named as 1-methyl-2-[(6Z,9Z,12Z)-6,9,12-pentadecatriene]-4(1H)-quinolone (1), together with three known quinolone alkaloids 1-methyl-2-[(6Z,9Z)-6,9-pentadecadienyl]-4(1H)-quinolone (2), 1-methyl-2-[(4Z,7Z)-4,7-tridecadienyl]-4(1H)-quinolone (3), 1-methyl-2-[(Z)-8-tridecenyl]-4(1H)-quinolone (4), were isolated from the fruits of Tetradium ruticarpum (A.Juss.) T.G.Hartley. Their structures were elucidated by physicochemical properties and spectroscopic data. All compounds were evaluated for their cytotoxic activities against three human tumor cell lines, including Lovo, MDA-MB-231, HeLa cells, by MTT method in 96-well microplates, and compounds 1 exhibited potent activity against MDA-MB-231 cells with IC50 values of 7.95 μM.