Antileishmanial activity and immunomodulatory effect of seco subamolide, a butanolide isolated from Nectandra oppositifolia (Lauraceae)

Abstract

Background: Visceral leishmaniasis is a complex neglected tropical disease caused by Leishmania donovani complex. Its current treatment reveals strong limitations, especially high toxicity. In this context, natural products are important sources of new drug alternatives for VL therapy. Therefore, the antileishmanial and immunomodulatory activity of compounds isolated from Nectandra oppositifolia (Lauraceae) was investigated herein.

Methods: The n-hexane extract from twigs of N. oppositifolia were subjected to HPLC/HRESIMS and bioactivity-guided fractionation to afford compounds 1 and 2 which were evaluated in vitro against Leishmania (L.) infantum chagasi and NCTC cells.

Results: The n-hexane extract displayed activity against L. (L.) infantum chagasi and afforded isolinderanolide E (1) and secosubamolide A (2), which were effective against L. (L.) infantum chagasi promastigotes, with IC₅₀ values of 57.9 and 24.9 µM, respectively. Compound 2 was effective against amastigotes (IC₅₀ = 10.5 µM) and displayed moderate mammalian cytotoxicity (CC₅₀ = 42 µM). The immunomodulatory studies of compound 2 suggested an anti-inflammatory activity, with suppression of IL-6, IL-10, TNF with lack of nitric oxide.

Conclusion: This study showed the antileishmanial activity of compounds 1 and 2 isolated from N. oppositifolia. Furthermore, compound 2 demonstrated an antileishmanial activity towards amastigotes associated to an immunomodulatory effect.

Keywords: Antileishmanial; Immunomodulatory; Leishmania (L.) infantum chagasi; Nectandra oppositifolia; Secosubamolide.

Figure 1.. HPLC/HRESIMS analysis of crude n-hexane extract from twigs of N. oppositifolia.

Figure 2.. Structures of compounds 1 and 2 isolated from twigs of N. oppositifolia.

Figure 3.. Effects of treatment of L. (L.) infantum chagasi-infected macrophages with secosubamolide A (compound 2) on the production of proinflammatory cytokines (TNF, MCP-1, IL-6, and IL-10). LPS was used as positive control, and macrophages without treatment were used as negative control. The results are expressed in pg/mL, and the mediators were measured by flow cytometry (BD-LSR FORTESSA) in the culture supernatants with the CBA kit assay (BD Mouse Inflammation Kit, USA). MØ: macrophages, MØI: Leishmania-infected macrophages. (IL-6) LPS production: MØ 8737 pg/mL, MØI 9060 pg/mL. (IL-10) LPS production: MØ 859 pg/mL, MØI 955 pg/mL. (MCP-1) LPS production: MØ 4769 pg/mL, MØI 5301 pg/mL. (TNF) LPS production: MØ 4973 pg/mL, MØI 5260 pg/mL.