During our continual investigations on Oldenlandia diffusa (Willd.) Roxb., two new iridoid glucosides, diffusosides C (1) and D (2), were isolated and their structures were elucidated through cumulative analysis of NMR and HRESIMS spectroscopic data as well as computational studies. Both isolated compounds displayed no obvious neuroprotective activity on H₂O₂-induced injury PC12 cells at 50 μM in vitro. Graphical Abstract

Objective: The fungicidal activity of 86 monoterpene indole alkaloids (MIAs) derived from plants was evaluated to identify novel lead compounds with antifungal potential. Methods: In this study, both in vitro and in vivo antifungal assays were performed to assess the efficacy of the selected MIAs. Results and Discussion: Among the tested compounds, rhazinilam (32) and rhazinal (33) exhibited markedly stronger antifungal activity against Aspergillus niger than ketoconazole in preliminary screenings. Further evaluation using mycelial growth inhibition assays confirmed that both compounds were significantly more active than ketoconazole against A. niger, B. dothidea, and F. oxysporum f. sp. cubense in vitro. The IC₅₀ values for rhazinilam (32) were < 5, < 10, and 17.89 μg/mL, respectively; for rhazinal (33), the values were < 2.5, < 5, and < 5 μg/mL, respectively. Moreover, in vivo tests on cucumber leaves demonstrated that at a concentration of 40 μg/mL, compounds (32) and (33) provided significant protection against A. niger, with protection rates of 77.27 and 100%, respectively, compared to 47.62% for ketoconazole. Conclusions: Rhazinilam (32) and rhazinal (33) demonstrated potent antifungal activity in both in vitro and in vivo experiments, highlighting their promise as lead candidates for the development of novel fungicidal agents.