Two cyclotetrapeptides, henceforth named Provipeptides A (1) and B (2), along with five known diketopiperazines (3–7) were isolated from the liquid culture of marine Streptomyces sp. 161a recovered from a sample of sea grass Bryopsis sp. The structures of cyclotetrapeptides and diketopiperazines (DKPs) were established by 1D and 2D NMR data, MS, and by comparison with literature data. The absolute stereochemistry of compounds cyclo-(l-Pro-l-Leu-d-Pro-l-Phe) 1 and cyclo-(-Pro-Ile-Pro-Phe) 2 was established by the Marfey’s method. Compound 1 showed antibacterial activity against rice phytopathogenic strains Burkholderia glumae (MIC = 1.1 mM) and Burkholderia gladioli (MIC = 0.068 mM), compound 2 was active only against B. glumae (MIC = 1.1 mM), and DKP cyclo-[l-Pro-l-Leu] 5 showed to be active against B. gladioli (MIC = 0.3 mM) and B. glumae (MIC = 2.4 mM). Compounds 1 and 2 showed 65% and 50% inhibition of Colletotrichum gloeosporioides (yam pathogen) conidia germination, respectively at a concentration of 1.1 mM.

Three new diterpene alkaloids, (+)-8-epiagelasine T (1), (+)-10-epiagelasine B (2), and (+)-12-hydroxyagelasidine C (3), along with three known compounds, (+)-ent-agelasine F (4), (+)-agelasine B (5), and (+)-agelasidine C (6), were isolated from the sponge Agelas citrina, collected on the coasts of the Yucatán Peninsula (Mexico). Their chemical structures were elucidated by 1D and 2D NMR spectroscopy, HRESIMS techniques, and a comparison with literature data. Although the synthesis of (+)-ent-agelasine F (4) has been previously reported, this is the first time that it was isolated as a natural product. The evaluation of the antimicrobial activity against the Gram-positive pathogens Staphylococcus aureus, Streptococcus pneumoniae, Enterococcus faecalis showed that all of them were active, with (+)-10-epiagelasine B (2) being the most active compound with an MIC in the range of 1–8 µg/mL. On the other hand, the Gram-negative pathogenes Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae were also evaluated, and only (+)-agelasine B (5) showed a moderate antibacterial activity with a MIC value of 16 μg/mL.

Diatraea species are considered the most important insect pests in sugarcane crops in Colombia and other South America countries. Previous research demonstrated Beauveria bassiana isolate Bv062 to be pathogenic to larvae of Diatraea species under laboratory conditions. However, virulence of the isolate was variable, possibly affected by inoculum quality. The aim of this research was to select an appropriate mass culture medium to produce conidia with consistently high yield, high virulence, and high storage stability. Conidia were produced on three semi-solid media based on rice, oat and potato, which were adjusted to three levels of water activity (a_w). Conidia yield, germination, polyols accumulation, enzymatic activity, and virulence to Diatraea saccharalis larvae, before and after 30 days of storage at 30°C, were measured. Conidia produced on potato-based medium were the most virulent, with a median lethal time (LT₅₀) of 8.9 days, compared to 9.7 and 9.1 days for rice and oat media, respectively. Insecticidal activity was stable after one month of storage for conidia produced on potato (LT₅₀ 8.0 days) but was reduced for conidia produced on the other media (LT₅₀ 13.0 days and 11.7 days for rice and oat, respectively). Mannitol was the predominant polyol in conidia and trehalose was not detected. Maximum yield and storage stability were obtained in the potato-based medium (C:N ratio of 30:1). Based on these results, potato-based medium is superior to the standard rice-based medium for the production of B. bassiana Bv062 conidia with better ecophysiological performance to control the sugar cane borer.

The Caribbean soft coral Erythropodium caribaeorum is a rich source of erythrolides—chlorinated briarane diterpenoids. These compounds have an ecological role as feeding deterrents, with a wide variation in their composition depending on the location where the sample is collected. In Colombia, this soft coral can be found at different locations in the Caribbean Sea including Santa Marta, Islas del Rosario, and Providencia—three environmentally different coral reef areas in the south and southwest Caribbean Sea. In order to evaluate differences in erythrolide composition, the metabolic profiles of samples from each of these locations were analyzed by HPLC-MS. Principal component analysis showed changes in the diterpene composition according to the sample origin. Diterpenes from samples collected at each location were isolated to describe the three chemotypes. The chemotype from Santa Marta was highly diverse, with the new erythrolides W and X together with eight known erythrolides. The sample from Islas del Rosario showed a low diversity chemotype constituted by high amounts of erythrolide A and B. The chemotype from Providencia showed low chemical diversity with only two main compounds—erythrolide V and R. Evaluation of cytotoxic activity against the human cancer cell lines PC-3, MCF7, and A549 showed erythrolides A and B as the more active compounds with IC₅₀ values in the range from 2.45 to 30 μM.