Records of Natural Products

The Beibu Gulf represents an underexplored reservoir of marine micro-/organisms and secondary metabolites. Three uncommon 4-hydroxy-2-pyridone alkaloids and one phenazine alkaloid were obtained from the Beibu Gulf coral-associated fungus Acremonium sclerotigenum GXIMD 02501 via OSMAC approach. They were identified as campyridones D (1) and A (2), ilicicolin H (3), and phenazine-1-carboxylic acid (4), respectively, by spectroscopic analysis and comparison with literature values. All of them were evaluated for cytotoxic, anti-Vibrio, and NF-κB luciferase inhibitory activities. Compounds 2 and 3 showed cytotoxicity against two prostate cancer cell lines, with IC50 values of 17.6 ± 1.3 and 5.5 ± 1.2 μM for PC-3, while 25.4 ± 1.7 and 11.9 ± 1.3 μM for 22Rv1, respectively. Besides, compound 4 showed promising anti-Vibrio activity with MIC values of 0.047–0.067 mg/mL and also displayed inhibition of LPS-induced NF-κB activation at 10 μM.

Chemical investigation of the EtOAc extract of a deep-sea-derived fungus Penicillium thomii Maire YPGA3 cultured on rice solid medium led to the isolation of three new chromone analogs, named penithochromones U-W (1-3), along with six known compounds (4-9). The structures were determined by extensive analyses of spectroscopic data (NMR and HRESIMS data). Compounds 1-3 are 5,7-dioxygenated chromone analogs bearing an aliphatic acid side chain. All isolated compounds were inactive toward the a-glucosidase at the concentration of 200 mM.

The first phytochemical study of Elaeocarpus apiculatus led to the isolation of five compounds, including two furan derivatives (1 and 2) and three amides (3-5). Among them, compound 1 was a new furan derivative, and compounds 2-5 were discovered from the genus Elaeocarpus for the first time. The characterization of these compounds was achieved by HRMS, UV, IR and NMR data. Compounds 1, 3 and 4 showed weak nitric oxide (NO) inhibitory effects. A potential biogenetic pathway for the formation of 1 was proposed.

One neo-clerodane diterpenoid (1), two abietane diterpenoids (2 and 3), three flavonoids (3–6), one C6-substituted chromone derivative (7), one phenylpropanoid (8), as well as one chain fatty acid (9) were isolated from the whole plants of Ajuga nipponensis. Their structures were established by detailed analysis of the HRESIMS, 1D and 2D NMR, UV, and IR. The absolute configuration of compound 1 was firstly determined by ECD calculation and single crystal diffraction. The NMR data of compound 9 are reported for the first time. Compounds 4, 7–9 were isolated from this medicinal plant for the first time, and 4, 9 were first discovered from natural products. The isolates 1–7 were tested for their antioxidant and mushroom tyrosinase inhibitory activities. Most of them showed moderate antioxidant activities. Compounds 1, 4, 5, and 7 exhibited obvious antioxidant activities at 50 μM, with % inhibition values of 32.37±0.75%, 25.30±0.66%, 28.76±0.64%, 31.06±0.46%, respectively, with L-ascorbic acid used as the positive control (71.29±0.34%). Compound 7 exhibited significant inhibitory activities against mushroom tyrosinase (%inhibition values of 16.94±1.28%), with arbutin used as the positive control (29.9±0.99%).