Anti-mycobacterial and anti-inflammatory activity of restinga plants: a dual approach in searching for new drugs to treat severe tuberculosis

Exploring the Antimycobacterial Potential of Podocarpusflavone A from Kielmeyera membranacea: In Vitro and In Vivo Insights

Background/Objectives: Tuberculosis (TB) is one of the leading infectious causes of death worldwide, highlighting the importance of identifying new anti-TB agents. In previous research, our team identified antimycobacterial activity in Kielmeyera membranacea leaf extract; therefore, this study aims to conduct further exploration of its potential. Methods: Classical chromatography was applied for fractionation and spectrometric techniques were utilized for chemical characterization. For in vitro tests, samples were assessed against Mycobacterium tuberculosis and Mycobacterium marinum. The toxicity and efficacy of active samples were evaluated in vivo using different zebrafish models. Chemogenomics studies were applied to predict the isolated active compound's potential mode of action. Results: We performed fractionation of K. membranacea ethanolic extract (EE) and then its dichloromethane fraction (DCM), and the biflavonoid podocarpusflavone A (PCFA) was isolated and identified as a promising active compound. The EE and PCFA were found to be non-toxic to zebrafish larvae and were able to inhibit M. tuberculosis growth extracellularly. Additionally, PCFA demonstrated antimycobacterial activity within infected macrophages, especially when combined with isoniazid. In addition, the EE, DCM, and PCFA have shown the ability to inhibit M. marinum's growth during in vivo zebrafish larvae yolk infection. Notably, PCFA also effectively countered systemic infection established through the caudal vein, showing a similar inhibitory activity profile to rifampicin, both at 32 µM. A reduction in the transcriptional levels of pro-inflammatory cytokines confirmed the infection resolution. The protein tyrosine phosphatase B (PtpB) of M. tuberculosis, which inhibits the macrophage immune response, was predicted as a theoretical target of PCFA. This finding is in agreement with the higher activity observed for PCFA intracellularly and in vivo on zebrafish, compared with the direct action in M. tuberculosis. Conclusions: Here, we describe the discovery of PCFA as an intracellular inhibitor of M. tuberculosis and provide evidence of its in vivo efficacy and safety, encouraging its further development as a combination drug in novel therapeutic regimens for TB.

Antitumoral effect thought ROS production of the sesquiterpene lactone centratherin isolated from Eremanthus crotonoides, an endemic plant from Brazil

Cancer is a global public health problem, requiring the development of new and more effective drugs for treatment. Eremanthus crotonoides, is a common plant found in the Brazilian Cerrado and Atlantic Forest and is used as a traditional medicinal plant in some regions. This study evaluated the potential antitumor effect of centratherin, a compound isolated from E. crotonoides leaves, against cancer cells. In colorectal cancer cells, centratherin showed greater toxicity than carboplatin while maintaining comparable selectivity to the control. Although centratherin did not induce classical apoptotic phenotypes and was not inhibited by Zvad, it did induce elevated levels of reactive oxygen species (ROS) that was responsible for cell death explaining its toxicity. in silico analysis, showed that this substance has high oral bioavailability and intestinal absorption. Centratherin was found to be selective against colon cancer cells and, therefore may be considered for future studies on colorectal cancer (CRC) studies.

Natural products from Vitex polygama and their antimycobacterial and anti-inflammatory activity

Tuberculosis (TB) remains a worldwide public health threat because of the emergence of resistant strains and subsequent inappropriate response to current therapy. We have been studying the restinga plants' antimycobacterial and anti-inflammatory potential. Dichloromethane fraction (DCM) from Vitex polygama Cham. showed high activity against Mycobacterium tuberculosis (Mtb) H37Rv. In this context, DCM fraction and isolated compounds were investigated against Mtb H37Rv and M299 (MDR strain) and for their immunomodulatory and cytotoxicity actions. Orientin showed the best antimycobacterial effect against Mtb M299 MDR strain (MIC₅₀ 15.4 ± 1.6 µg/mL), capacity of inhibiting NO production by macrophages (IC₅₀ 6.5 ± 1.2 µg/mL) and no significant cytotoxicity. The antimycobacterial effect of orientin was also observed on Mtb H37Rv intracellular growth in RAW 264.7 macrophages (MIC₅₀ 3.5 ± 1.1 and MIC₉₀ 9.1 ± 1.0 µg/mL). This is the first report describing the antimycobacterial effect of orientin, in both extra- and intracellular growth.