Antiprotozoal Compounds from Urolepis hecatantha (Asteraceae)

Trypanocidal and Anti-Inflammatory Effects of Three ent-Kaurane Diterpenoids from Gymnocoronis spilanthoides var. subcordata (Asteraceae)

Chagas disease, caused by the protozoan Trypanosoma cruzi, affects 6-7 million people worldwide. The dichloromethane extract obtained from the aerial parts of Gymnocoronis spilanthoides var subcordata showed trypanocidal activity in vitro. The fractionation of the dewaxed organic extract via column chromatography led to the isolation of three diterpenoids: ent-9α,11α-dihydroxy-15-oxo-kaur-16-en-19-oic acid or adenostemmoic acid B, (16R)-ent-11α-hydroxy-15-oxokauran-19-oic acid and ent-11α-hydroxy-15-oxo-kaur-16-en-19-oic acid. These compounds showed IC50 values of 10.6, 15.9 and 4.8 µM against T. cruzi epimastigotes, respectively. When tested against amastigotes, the diterpenoids afforded IC50 values of 6.1, 19.5 and 60.6 µM, respectively. The cytotoxicity of the compounds was tested on mammalian cells using an MTT assay, resulting in CC50s of 321.8, 23.3 and 14.8 µM, respectively. The effect of adenostemmoic acid B on T. cruzi was examined at the ultrastructural level using transmission microscopy. Treatment with 20 μM for 48 h stimulated the formation of abnormal cytosolic membranous structures in the parasite. This compound also showed an anti-inflammatory effect in murine macrophages stimulated with LPS and other TLR agonists. Treatment of macrophages with adenostemmoic acid B was able to reduce TNF secretion and nitric oxide production, while increasing IL-10 production. The combination of adenostemmoic acid B with benznidazole resulted in greater inhibition of NF-kB and a decrease in nitrite concentration. The administration of adenostemmoic acid B to mice infected with trypomastigotes of T. cruzi at the dose of 1 mg/kg/day for five days produced a significant decrease in parasitemia levels and weight loss. Treatment with the association with benznidazole increased the survival time of the animals. In view of these results, adenostemmoic acid B could be considered a promising candidate for further studies in the search for new treatments for Chagas disease.

Anti-Trypanosoma cruzi Properties of Sesquiterpene Lactones Isolated from Stevia spp.: In Vitro and In Silico Studies

Stevia species (Asteraceae) have been a rich source of terpenoid compounds, mainly sesquiterpene lactones, several of which show antiprotozoal activity. In the search for new trypanocidal compounds, S. satureiifolia var. satureiifolia and S. alpina were studied. Two sesquiterpene lactones, santhemoidin C and 2-oxo-8-deoxyligustrin, respectively, were isolated. These compounds were assessed in vitro against Trypanosoma cruzi stages, showing IC₅₀ values of 11.80 and 4.98 on epimastigotes, 56.08 and 26.19 on trypomastigotes and 4.88 and 20.20 µM on amastigotes, respectively. Cytotoxicity was evaluated on Vero cells by the MTT assay. The effect of the compounds on trypanothyone reductase (TcTR), Trans-sialidase (TcTS) and the prolyl oligopeptidase of 80 kDa (Tc80) as potential molecular targets of T. cruzi was investigated. Santhemoidin C inhibited oligopeptidase activity when tested against recombinant Tc80 using a fluorometric assay, reaching an IC₅₀ of 34.9 µM. Molecular docking was performed to study the interaction between santhemoidin C and the Tc80 protein, reaching high docking energy levels. Plasma membrane shedding and cytoplasmic vacuoles, resembling autophagosomes, were detected by transmission microscopy in parasites treated with santhemoidin C. Based on these results, santhemoidin C represents a promising candidate for further studies in the search for new molecules for the development of trypanocidal drugs.

Phenolic Profile and Cholinesterase Inhibitory Properties of Three Chilean Altiplano Plants: Clinopodium gilliesii (Benth.) Kuntze [Lamiaceae], Mutisia acuminata Ruiz & Pav. var. hirsuta (Meyen) Cabrera, and Tagetes multiflora (Kunth) [Asteraceae]

This research aimed to identify the phenolic profile and composition of the aerial parts of three native species used in traditional medicine in the Andean Altiplano of northern Chile: Clinopodium gilliesii (Benth.) Kuntze [Lamiaceae] (commonly known as Muña-Muña), Mutisia acuminata Ruiz & Pav. var. hirsuta (Meyen) Cabrera [Asteraceae] (commonly known as Chinchircoma), and Tagetes multiflora (Kunth), [Asteraceae] (commonly known as Gracilis), as well as to evaluate their potential inhibitory effects against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Polyphenolic enriched-extracts (PEEs) of the species were prepared and analyzed and the main components were quantified using HPLC-DAD. In total, 30 phenolic compounds were identified and quantified in all species, including simple phenolics, hydroxycinnamic acids, flavan-3-ols (monomers and polymers), flavanones, and flavonols. In addition, other main phenolics from the extracts were tentatively identified by ESI-MS-MS high-resolution analysis. T. multiflora extract showed the greatest anti-AChE and BChE activity in comparison with C. gilliesii and M. acuminata extracts, being the anti-AChE and BChE activity weak in all extracts in comparison to galantamine control. To comprise to better understand the interactions between cholinesterase enzymes and the main phenolics identified in T. multiflora, molecular docking analysis was conducted.

Plant Terpenoids as Hit Compounds against Trypanosomiasis

Human African trypanosomiasis (sleeping sickness) and American trypanosomiasis (Chagas disease) are vector-borne neglected tropical diseases, caused by the protozoan parasites Trypanosoma brucei and Trypanosoma cruzi, respectively. These diseases were circumscribed to South American and African countries in the past. However, human migration, military interventions, and climate changes have had an important effect on their worldwide propagation, particularly Chagas disease. Currently, the treatment of trypanosomiasis is not ideal, becoming a challenge in poor populations with limited resources. Exploring natural products from higher plants remains a valuable approach to find new hits and enlarge the pipeline of new drugs against protozoal human infections. This review covers the recent studies (2016–2021) on plant terpenoids, and their semi-synthetic derivatives, which have shown promising in vitro and in vivo activities against Trypanosoma parasites.

In Vitro Metabolism of Helenalin Acetate and 11α,13-Dihydrohelenalin Acetate: Natural Sesquiterpene Lactones from Arnica

Arnica tincture is a herbal medicinal preparation with anti-inflammatory activity which is used traditionally for the topical treatment of blunt injuries as well as rheumatic muscle and joint complaints. Its main bioactive constituents are sesquiterpene lactones (STLs) of the helenalin and 11α,13-dihydrohelenalin types. Besides the mentioned activity, the tincture and its isolated STLs have antileishmanial activity. In a recent in vivo study, a treatment with Arnica tincture cured cutaneous Leishmaniasis (CL) in a golden hamster model. CL is a neglected tropical disease affecting more than two million people every year, for which new treatments are urgently needed. In order to use Arnica tincture on open CL lesions of human patients, it is important to know how the constituents are metabolized. Therefore, in vitro metabolism experiments with liver microsomes of different species (rat, pig and human) were performed with the Arnica STLs helenalin acetate and 11α,13-dihydrohelenalin acetate. Phase I and phase II metabolism experiments were performed, as well as a combination of both. Glutathione conjugation plays a major role in the metabolism of these STLs, as could be expected based on previous reports on their reactivity. Besides glutathione conjugates, several other metabolites were formed, e.g., water conjugates and hydroxides. Our results show for the first time a detailed picture of the metabolism of Arnica STLs. The fast and extensive formation of glutathione conjugates makes it unlikely that low absorbed levels of these compounds, as expected after dermal absorption from Arnica tincture, could be of toxicological concern.

Stevia Genus: Phytochemistry and Biological Activities Update

The Stevia genus (Asteraceae) comprises around 230 species, distributed from the southern United States to the South American Andean region. Stevia rebaudiana, a Paraguayan herb that produces an intensely sweet diterpene glycoside called stevioside, is the most relevant member of this genus. Apart from S. rebaudiana, many other species belonging to the Stevia genus are considered medicinal and have been popularly used to treat different ailments. The members from this genus produce sesquiterpene lactones, diterpenes, longipinanes, and flavonoids as the main types of phytochemicals. Many pharmacological activities have been described for Stevia extracts and isolated compounds, antioxidant, antiparasitic, antiviral, anti-inflammatory, and antiproliferative activities being the most frequently mentioned. This review aims to present an update of the Stevia genus covering ethnobotanical aspects and traditional uses, phytochemistry, and biological activities of the extracts and isolated compounds.