A series of novel coumarin-3-carboxamide derivatives were designed and synthesized to evaluate their biological activities. The compounds showed little to no activity against gram-positive and gram-negative bacteria but specifically showed potential to inhibit the growth of cancer cells. In particular, among the tested compounds, 4-fluoro and 2,5-difluoro benzamide derivatives (14b and 14e, respectively) were found to be the most potent derivatives against HepG2 cancer cell lines (IC₅₀ = 2.62–4.85 μM) and HeLa cancer cell lines (IC₅₀ = 0.39–0.75 μM). The activities of these two compounds were comparable to that of the positive control doxorubicin; especially, 4-flurobenzamide derivative (14b) exhibited low cytotoxic activity against LLC-MK2 normal cell lines, with IC₅₀ more than 100 μM. The molecular docking study of the synthesized compounds revealed the binding to the active site of the CK2 enzyme, indicating that the presence of the benzamide functionality is an important feature for anticancer activity.

2,5-Diketopiperazine derivatives, consisting of benzylidene and alkylidene substituents at 3 and 6 positions, have been considered as a core structure for their antiviral activities. Herein, the novel N-substituted 2,5-Diketopiperazine derivatives were successfully prepared and their antiviral activities against influenza virus were evaluated by monitoring viral propagation in embryonated chicken eggs. It was found that (3Z,6Z)-3-benzylidene-6-(2-methyl propylidene)-4-substituted-2,5-Diketopiperazines (13b–d), (3Z,6E)-3-benzylidene-6-(2-methylpropyli dene)-1-(1-ethyl pyrrolidine)-2,5-Diketopiperazine (14c), and Lansai-C exhibited negative results in influenza virus propagation at a concentration of 25 µg/mL. Additionally, molecular docking study revealed that 13b–d and 14c bound in 430-cavity of neuraminidase from H5N2 avian influenza virus and the synthesized derivatives also strongly interacted with the key amino acid residues, including Arg371, Pro326, Ile427, and Thr439.

A series of tetrahydro-ß-carbolines substituted with an alkyl or acyl side chain was synthesized and screened for its antifungal activity against plant pathogenic fungi (Bipolaris oryzae, Curvularia lunata, Fusarium semitectum, and Fusarium fujikuroi). The structure activity relationship revealed that the substituent at the piperidine nitrogen plays an important role for increasing antifungal activities. In this series, 2-octyl-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole (3g) displayed potent antifungal activities with a minimum inhibitory concentration of 0.1 μg/mL, including good inhibitory activity to the radial growth of fungus at a concentration of 100 μg/mL compared to amphotericin B.

Methyl-5-(hydroxymethyl)-2-furan carboxylate and derivatives were prepared from furfuryl alcohol and their biological activities were studied for cytotoxicity against cancer cell lines HeLa, HepG2 and Vero, and Gram (+) and Gram (-) bacteria. The amine derivative, (5-(((2-(1H-indol-3-yl)ethyl)amino)methyl) furan-2-yl)methyl acetate, was found to have the most potent biological activity with IC50 62.37 µg/mL against the HeLa cell line and MIC 250 µg/mL against the photogenic bacteria.

Marine macroalgae host endophytic microbial communities that serve as valuable reservoirs for drug discovery. In this study, the endophytic actinomycete Streptomyces sp. UL09 was isolated from the internal thallus tissues of the green macroalga Ulva rigida C. Agardh. Fermentation of strain UL09 yielded the nitrobenzoyl sesquiterpenoids insulicolide B (1.63 mg/L) and insulicolide C (1.79 mg/L). The planar structures of compounds 1 and 2 were assigned as insulicolides B and C, respectively, via spectroscopic analysis and comparison with literature data. In vitro bioassays revealed moderate activity against Gram-positive bacteria (MIC 128–512 µg/mL), including MRSA Sp3 (MIC 128–256 µg/mL). These compounds exhibited cytotoxic activity against human cancer cell lines (HeLa, HepG2, and MDA-MB-231) with IC ₅₀ values ranging from 34.35 to 142.64 µg/mL. Both compounds demonstrated lower cytotoxicity toward non-malignant Vero cells. Molecular docking simulations predicted that both metabolites target the catalytic ATP-binding cleft of human Polo-like kinase 1 (Plk1), with insulicolide B displaying a favorable docking score (ΔG = -9.273 kcal/mol). Furthermore, pkCSM predicted high intestinal absorption and no alerts for the assessed toxicity endpoints. These findings establish Streptomyces sp. UL09 as a viable alternative biological source of insulicolides B and C, highlighting their potential as leads for oncology applications.