Molecular modelling and anticholinesterase activity of the essential oil from three chemotypes of Lippia alba (Mill.) N.E.Br. ex Britton & P. Wilson (Verbenaceae).

Lippia alba (Mill.) N.E. Brown (Verbenaceae), popularly known as "erva cidreira", is one of the most used plants in Brazilian folk medicine. The species has several chemotypes and its volatile constituents have already been characterized, and present different chemical markers with known pharmacological properties, such as analgesic, sedative and antifungal properties. The objective of this study was to evaluate the anticholinesterase activity (AChE) of the essential oil of three chemotypes of Lippia alba and, by using molecular anchoring, determine the best receptor-ligand interaction energies of the main constituents present in the samples of oil. The essential oils were obtained via hydrodistillation (LA1 and LA2) and steam drag (LA3), and their volatile constituents determined using GC-MS. For the determination of anticholinesterase activity, direct bioautography and colorimetry assays based on Ellman's method were used. Molecular docking was performed using a multiple solution genetic algorithm and Merck molecular force field 94 (MMFF94) as the scoring function. In the main constituents of the oil samples, three chemotypes were identified for L. alba: LA1 is rich in citral, LA2 is rich in carvone and LA3 is rich in linalool. All L. alba chemotypes showed AChE enzyme inhibition with an IC50 of 3.57 µg/mL (LA1), 0.1 µg/mL (LA2) and 4.34 µg/mL (LA3). The molecular docking study complemented the results of the experiment and demonstrated significant interactions between the main constituents of the oils and the amino acid residues of the AChE enzyme. Irrespective of the chemotype, Lippia alba presents biotechnological potential for the discovery of anticholinesterase substances, with the chemotype LA2 (rich in carvone) being the most active.

In Vitro and in Vivo Antimalarial Activity, Cytotoxicity and Phytochemical HRMS2 Profile of Plants from the Western Pará State, Brazilian Amazonia.

Ethnopharmacology and botanical taxonomy are valid criteria used to selecting plants for antimalarial bioprospection purposes. Based on these two criteria, ethanol extracts of 11 plants from Santarém City vicinities, Western Pará State, Brazilian Amazonia, had their in vitro antiplasmodial activity against chloroquine-resistant Plasmodium falciparum (W2 clone) assessed by the PfLDH method, whereas their cytotoxicity to HepG2-A16 cells was assessed through MTT assay. Acmella oleracea, Siparuna krukovii and Trema micrantha extracts disclosed the highest rate of parasite growth inhibition (90 %) in screening tests. In vivo antimalarial assays were conducted with these extracts against Plasmodium berghei (NK 65 strain) infected mice. Inhibition rate of parasite multiplication ranged from 41.4 % to 60.9 % at the lowest extract dose (25 mg/kg). HPLC-ESI-HRMS2 analyses allowed the putative identification of alkylamides, fatty acids, flavonoid glycosides and alkaloids in ethanol extracts deriving from these three plant species. Results pointed towards A. oleracea flowers ethanol extract as the most promising potential candidate to preclinical studies aiming the development of antimalarial phytomedicine.

Brazilian plants with antimalarial activity: A review of the period from 2011 to 2022.

ETHNOPHARMACOLOGICAL RELEVANCE: Malaria continues to be a serious global public health problem in subtropical and tropical countries of the world. The main drugs used in the treatment of human malaria, quinine and artemisinin, are isolates of medicinal plants, making the use of plants a widespread practice in countries where malaria is endemic. Over the years, due to the increased resistance of the parasite to chloroquine and artemisinin in certain regions, new strategies for combating malaria have been employed, including research with medicinal plants. AIM: This review focuses on the scientific production regarding medicinal plants from Brazil whose antimalarial activity was evaluated during the period from 2011 to 2022. 2. METHODOLOGY: For this review, four electronic databases were selected for research: Pubmed, ScienceDirect, Scielo and Periódicos CAPES. Searches were made for full texts published in the form of scientific articles written in Portuguese or English and in a digital format. In addition, prospects for new treatments as well as future research that encourages the search for natural products and antimalarial derivatives are also presented. RESULTS: A total of 61 publications were encountered, which cited 36 botanical families and 92 species using different Plasmodium strains in in vitro and in vivo assays. The botanical families with the most expressive number of species found were Rubiaceae, Apocynaceae, Fabaceae and Asteraceae (14, 14, 9 and 6 species, respectively), and the most frequently cited species were of the genera Psychotria L. (8) and Aspidosperma Mart. (12), which belong to the families Rubiaceae and Apocynaceae. Altogether, 75 compounds were identified or isolated from 28 different species, 31 of which are alkaloids. In addition, the extracts of the analyzed species, including the isolated compounds, showed a significant reduction of parasitemia in P. falciparum and P. berghei, especially in the clones W2 CQ-R (in vitro) and ANKA (in vivo), respectively. The Brazilian regions with the highest number of species analyzed were those of the north, especially the states of Pará and Amazonas, and the southeast, especially the state of Minas Gerais. CONCLUSION: Although many plant species with antimalarial potential have been identified in Brazil, studies of new antimalarial molecules are slow and have not evolved to the production of a phytotherapeutic medicine. Given this, investigations of plants of traditional use and biotechnological approaches are necessary for the discovery of natural antimalarial products that contribute to the treatment of the disease in the country and in other endemic regions.

Evaluation of the anti-snakebite, antimicrobial and antioxidant potential of Philodendron megalophyllum Schott (Araceae), traditionally used in accidents caused by snakes in the western region of Pará, Brazil.

ETHNOPHARMACOLOGICAL RELEVANCE: In the region of Western Pará, Amazonia, Brazil, Philodendron megalophyllum is widely used for the treatment of envenomations caused by bites from venomous snakes. The traditional use of plants is usually done through oral administration of an infusion (decoction) soon after the bite occurs. The efficiency of aqueous extracts of P. megalophyllum was demonstrated for blocking the activity of the venom of Bothrops sp., but only for a pre-incubation protocol (venom:extract), which fails to simulate the real form of use of this species. In this context, the objective of this research was to evaluate the anti-snakebite potential of the aqueous extract of P. megalophyllum to inhibit for the biological activity induced by Bothrops atrox venom (BaV) using traditional treatment methods. MATERIAL AND METHODS: Initially, an aqueous extract using the stem of P. megalophyllum (AEPm) was prepared following the standard procedure used by the residents of the rural area along the Tapajós River (Eixo Forte region) in Santarém, PA, Brazil. The phytochemical profile of AEPm was conducted using thin layer chromatography (TLC) and phenolic compounds were quantified through colorimetric trials. The cytotoxicity of AEPm was evaluated using the MRC-5 human fibroblast line, and the antioxidant potential was measured using DPPH methods and cell culture. AEPm antimicrobial action was evaluated by the 96-well plate microdilution and the minimum inhibitory concentration (MIC) methods using 18 types of microorganisms including bacteria that are present in the oral cavity of snakes. AEPm blocking potential was tested against BaV activity in vitro (fibrinolytic) and in vivo (defibrinating and hemorrhagic). In order to test for an interaction between BaV and AEPm SDS-PAGE electrophoresis was conducted. RESULTS: The presence of coumarins, fatty acids, and hydrolysable tannins were detected in the AEPm. The colorimetric trials showed that AEPm had a high concentration of condensed tannins (20.1 ± 1.2%). The potential of AEPm for blocking of hemorrhagic and fibrinolytic activity of BaV showed a maximum reduction of 86.1% and 96.5%, respectively, for the pre-incubation protocol (1:10, venom:extract). However, when the extract was administered orally there was no significant blocking of these activities. The interaction of BaV and AEPm showed a modification of the profile of proteic bands when compared to the pattern of bands obtained from the BaV alone. The AEPm was not considered toxic, demonstrated antioxidant activity, and was capable of reducing the growth of 10 of the 18 studied microorganisms. CONCLUSION: Although the stem of P. megalophyllum is indicated by traditional medicine techniques as effective against snakebites, the extract, when tested orally was not able to significantly inhibit (p ˃ 0.05) hemorrhage and defibrinating activity induced by the B. atrox venom. On the other hand, the extract yielded a promising result with respect to antioxidant and antimicrobial potential, and after further studies it could be used as a complementary treatment for localized action and secondary infections that frequently occur with snakebites from the genus of Bothrops sp.

The inhibitory potential of the condensed-tannin-rich fraction of Plathymenia reticulata Benth. (Fabaceae) against Bothrops atrox envenomation.

ETHNOPHARMACOLOGICAL RELEVANCE: Ethnobotanical studies have shown that Plathymenia reticulata Benth. (Fabaceae) has been widely used in cases of snake envenomation, particularly in Northern Brazil. In light of this, the aim of this study was to evaluate the inhibitory potential of the condensed-tannin-rich fraction obtained from the bark of P. reticulata against the main biological activities induced by Bothrops atrox venom (BaV). MATERIALS AND METHODS: The chemical composition of the aqueous extract of P. reticulata (AEPr) was first investigated by thin-layer chromatography (TLC) and the extract was then fractionated by column chromatography on Sephadex LH-20. This yielded five main fractions (Pr1, Pr2, Pr3, Pr4 and Pr5), which were analyzed by colorimetry to determine their concentrations of total phenolics, total tannins and condensed tannins and to assess their potential for blocking the phospholipase activity of BaV. The Pr5 fraction was defined as the fraction rich in condensed tannins (CTPr), and its inhibitory potential against the activities of the venom was evaluated. CTPr was evaluated in different in vivo and in vitro experimental protocols. The in vivo protocols consisted of (1) pre-incubation (venom:CTPr, w/w), (2) pre-treatment (orally administered) and (3) post-treatment (orally administered) to evaluate the effect on the hemorrhagic and edematogenic activities of BaV; in the in vitro protocol the effect on phospholipase and coagulant activity using pre-incubation in both tests was evaluated. RESULTS: There was statistically significant inhibition (p<0.05) of hemorrhagic activity by CTPr when the pre-incubation protocol was used [55% (1:5, w/w) and 74% (1:10, w/w)] and when pre-treatment with doses of 50 and 100mg/kg was used (19% and 13%, respectively). However, for the concentrations tested, there was no statistically significant inhibition in the group subjected to post-treatment administered orally. CTPr blocked 100% of phospholipase activity and 63.3% (1:10, w/w) of coagulant activity when it was pre-incubated with BaV. There was a statistically significant reduction (p<0.05) in edema induced by BaV in the oral protocols. Maximum inhibition was 95% (pre-treatment). CONCLUSION: Our findings indicate that CTPr could be a good source of natural inhibitors of the components of snake venom responsible for inducing local inflammation.

Plants used to treat snakebites in Santarém, western Pará, Brazil: an assessment of their effectiveness in inhibiting hemorrhagic activity induced by Bothrops jararaca venom.

ETHNOPHARMACOLOGICAL RELEVANCE: The poor distribution and limited availability of antivenoms in Brazil have led to greater use of plants to treat snakebites. Very often such plants are the only alternative available to riverside communities. MATERIALS AND METHODS: Direct questionnaire-based interviews were conducted with members of the Cucurunã, São Pedro and Alter do Chão communities in Santarém, Pará, Brazil. For each of the 12 most frequently mentioned species aqueous extracts were prepared and the phytochemical profiles determined by thin layer chromatography. The concentrations of phenolic compounds (tannins and flavonoids) in the aqueous extracts were determined by colorimetric assays. To assess inhibition of the hemorrhagic activity of Bothrops jararaca venom, solutions containing the venom mixed with aqueous extracts in the ratios 1:12 and 1:48 were tested (w/w). SDS-PAGE and Western blot were used to assess the action of the extracts on Bothrops jararaca venom. RESULTS: In all, 24 plants belonging to 19 families were mentioned in the survey as being used to treat snakebites. Leaves (84%), seeds (60.9%) and inner bark (53%) were cited as the most frequently used parts in folk remedies, which were usually prepared in the form of a decoction (62.5%), tincture (45%) or maceration (22.5%). Hemorrhage induced by Bothrops jararaca venom was completely inhibited by aqueous extracts of Bellucia dichotoma, Connarus favosus, Plathymenia reticulata and Philodendron megalophyllum, which had a high phenolic content and contained condensed and hydrolyzable tannins. The results of SDS-PAGE showed that some venom protein bands were not visible when the venom was preincubated with the extracts that had completely inhibited hemorrhagic activity of the venom. Western blot showed that the extracts did not have any enzymatic action on the proteins in the venom as it failed to detect low-molecular-weight bands, which are indicative of possible enzymatic cleavage. CONCLUSIONS: Traditional use of plants to treat snakebites is a common practice in the western region of Pará, Brazil. Our findings show that some plant extracts were able to inhibit snake venom-induced hemorrhage in vitro. In vivo studies are being carried out to validate the traditional use of these species to treat snakebites.

A comparison of the ability of Bellucia dichotoma Cogn. (Melastomataceae) extract to inhibit the local effects of Bothrops atrox venom when pre-incubated and when used according to traditional methods.

Bellucia dichotoma Cogn. (Melastomataceae) is one of various plant species used in folk medicine in the west of the state of Pará, Brazil, to treat snake bites. Many studies have been carried out to evaluate the effectiveness of anti-snake bite plants, but few of these use the same preparation methods and doses as those traditionally used by the local populations. This study therefore compared inhibition of the main local effects of B. atrox venom (BaV) by aqueous extract of B. dichotoma (AEBd) administered according to traditional methods and pre-incubated with BaV). The concentrations of phenolic compounds (tannins and flavonoids) in AEBd were determined by colorimetric assays. The effectiveness of AEBd in inhibiting the hemorrhagic and edematogenic activities of BaV was evaluated in mice in four different experimental in vivo protocols: (1) pre-incubation (venom:extract, w/w); (2) pre-treatment (p.o.); (3) post-treatment (p.o.); and (4) AEBd (p.o.) in combination with Bothrops antivenom (BA) (i.v.). To assess in vitro inhibition of BaV phospholipase A2 activity, the pre-incubation method or incorporation of AEBd or BA in agarose gels were used. The effect of AEBd on BaV was determined by SDS-PAGE, zymography and Western blot. Colorimetric assays revealed higher concentrations of (condensed and hydrolyzable) tannins than flavonoids in AEBd. Hemorrhagic activity was completely inhibited using the pre-incubation protocol. However, with pre-treatment there was no significant inhibition for the concentrations tested, and with the post-treatment only the 725 mg/kg dose of AEBd was able to inhibit 40.5% (p = 0.001) of the hemorrhagic activity of BaV. Phospholipase A2 activity was only inhibited when AEBd was pre-incubated with BaV. BaV-induced edema was completely inhibited with pre-incubation (p < 0.05) and significantly reduced (p < 0.05) with pre- and post-treatment (p.o.) for the concentrations tested. The reduction in local edema was even greater when AEBd was administered in combination with BA. The SDS-PAGE profiles showed that several of the BaV protein (SDS-PAGE) and enzyme (zymography) bands were not detected when the venom was pre-incubated, and Western blot revealed that this was not caused by the AEBd enzymes observed in the zymogram. The "pseudo inhibition" observed after pre-incubation in this study may be due to the presence of tannins in the extract, which could act as chelating agents, removing metalloproteins and Ca²âº ions and thus inhibiting hemorrhagin and PLA2 activity. However, when administered according to traditional methods, B. dichotoma extract was effective in blocking BaV-induced edematogenic activity and had an additional effect on inhibition of this activity by BA.