Evaluación del efecto inhibitorio del veneno de Bothrops asper (mapaná), por los extractos obtenidos de hojas de Renealmia alpinia Rottb. Maas (Zingiberaceae), una especie botánica con propiedades antiofídicas y analgésicas

Plants and Phytocompounds Active Against Bothrops Venoms

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Snakebite envenomation is an important health problem in tropical countries, with severe human and social consequences. In Latin America, the Bothrops species constitute the main threat to humans, and the envenomation caused by these species quickly develops into severe local tissue damage, including swelling, hemorrhaging, myonecrosis, skin ulceration, and pain. The systemic effects of envenomation are usually neutralized by antivenom serum therapy, despite its intrinsic risks. However, neutralization of local tissue damage remains a challenge. To improve actual therapy, two major alternatives are proposed: the rational design of new specific antibodies for most of the tissue damaging/ poor immunogenic toxins, or the search for new synthetic or natural compounds which are able to inhibit these toxins and complement the serum therapy. Natural compounds isolated from plants, mainly from those used in folk medicine to treat snakebite, are a good choice for finding new lead compounds to improve snakebite treatment and minimize its consequences for the victims. In this article, we reviewed the most promising plants and phytocompounds active against bothropic venoms.

Assessment of the anti-snakebite properties of extracts of Aniba fragrans Ducke (Lauraceae) used in folk medicine as complementary treatment in cases of envenomation by Bothrops atrox

ETHNOPHARMACOLOGICAL RELEVANCE

Extracts of leaves and bark of Aniba fragrans are used as tea (decoction) to treat snakebites in communities in the Brazilian Amazon. The aqueous extract of the leaves of A. fragrans has been proven to be effective against Bothrops venom, but only when pre-incubated with the venom. This study sought to assess the potential of different types of extract of this species to inhibit the biological activities of Bothrops atrox venom (BaV) when used the same way as in folk medicine. The main classes of secondary metabolites and the concentrations of phenolics in the extracts were also determined.

MATERIALS AND METHODS

Four types of extract of A. fragrans were prepared: aqueous extract of the leaf (AEL), aqueous extract of the bark (AEB), hydroalcoholic leaf extract (HLE) and extract of the residue from hydrodistillation of the leaf (ERHL). The phytochemical profiles of the aqueous extracts were determined using thin layer chromatography (TLC), and the concentrations of phenolics were measured by colorimetric assays. To investigate the potential of the extracts to inhibit the biological activities of BaV, in vitro tests for antiphospholipase and antifibrinolytic activities were performed. In vivo tests for antihemorrhagic and antidefibrinating activities were also carried out, as well as antimicrobial tests for activity against the main bacteria found in the oral cavity of snakes. Interaction between the extracts and the proteins in BaV was assessed by electrophoresis (SDS-PAGE) and Western blot (WB). The cytotoxicity of the extracts was assessed in a strain of MRC-5 human fibroblasts.

RESULTS

Terpenoids, flavonoids and condensed and hydrolysable tannins were detected in all the extracts. Metabolites such as coumarins, fatty acids and alkaloids were present in some extracts but not in others, indicating different phytochemical profiles. Phenolics content varied between extracts, and there were more tannins in AEB and HLE. In the in vitro tests, the extracts inhibited the phospholipase and fibrinolytic activities of BaV in the two ratios of venom to extract used. HLE exhibited effective antimicrobial action as it inhibited growth of 11 of the 15 bacteria investigated, including Morganella morganii, the main bacteria described in the oral cavity of snakes. The extracts failed to inhibit the defibrinating activity of BaV, and only the Bothrops antivenom had a significant effect (96.1%) on this activity. BaV-induced hemorrhage was completely inhibited by AEL and AEB when the pre-incubation (venom:extract) protocol was used. When administered orally, as in folk medicine, both AEB and AEL produced significant inhibition of hemorrhagic activity (maximum inhibition 46.5% and 39.2%, respectively). SDS-PAGE and WB of the extracts pre-incubated with BaV showed that the main proteins in the venom had been precipitated by the extracts. None of the four extracts showed cytotoxic effects in the tests carried out with a human fibroblast cell line.

CONCLUSION

In addition to being effective in reducing hemorrhage when administered orally, the extracts displayed a high antimicrobial potential against microorganisms involved in secondary infections at the site of the snakebite. Once the extracts have been tested in accordance with the appropriate regulations, this species could potentially be used to produce a phytomedicine for complementary treatment of the secondary infections due to bacteria that aggravate the local signs and symptoms after snakebite envenomation.

Medicinal Plants for the Treatment of Local Tissue Damage Induced by Snake Venoms: An Overview from Traditional Use to Pharmacological Evidence

Snakebites are a serious problem in public health due to their high morbimortality. Most of snake venoms produce intense local tissue damage, which could lead to temporary or permanent disability in victims. The available specific treatment is the antivenom serum therapy, whose effectiveness is reduced against these effects. Thus, the search for complementary alternatives for snakebite treatment is relevant. There are several reports of the popular use of medicinal plants against snakebites worldwide. In recent years, many studies have been published giving pharmacological evidence of benefits of several vegetal species against local effects induced by a broad range of snake venoms, including inhibitory potential against hyaluronidase, phospholipase, proteolytic, hemorrhagic, myotoxic, and edematogenic activities. In this context, this review aimed to provide an updated overview of medicinal plants used popularly as antiophidic agents and discuss the main species with pharmacological studies supporting the uses, with emphasis on plants inhibiting local effects of snake envenomation. The present review provides an updated scenario and insights into future research aiming at validation of medicinal plants as antiophidic agents and strengthens the potentiality of ethnopharmacology as a tool for design of potent inhibitors and/or development of herbal medicines against venom toxins, especially local tissue damage.

The potential of aqueous extracts of Bellucia dichotoma Cogn. (Melastomataceae) to inhibit the biological activities of Bothrops atrox venom: A comparison of specimens collected in the states of Pará and Amazonas, Brazil

ETHNOPHARMACOLOGICAL IMPORTANCE

The effectiveness of aqueous extract of Bellucia dichotoma Cogn. (Melastomataceae) specimems collected in Santarém, PA, against some biological activities of Bothrops atrox venom (BaV) has been scientifically proven. Here, we analyzed the components and assessed the anti-snakebite potential of aqueous extracts of bark of B. dichotoma collected in Manaus, AM, (AEBd-MAO) and Santarém, PA, (AEBd-STM), both in Brazil.

MATERIALS AND METHODS

The phytochemical profiles of the aqueous extracts were identified using thin layer chromatography (TLC), and the concentrations of phenolics were determined by colorimetric assay. The inhibitory potential of the extracts was tested against the phospholipase A₂, coagulant and gelatinolytic activities of BaV in vitro and its defibrinating and edema-inducing activities in vivo. Interaction between BaV and the extracts was investigated using SDS-Page electrophoresis and Western blotting. Extract cytotoxicity and antioxidant potential were assessed using the human fibroblast cell line MRC-5 and the DPPH assay in cell culture, respectively.

RESULTS

While there was no difference between the phytochemical profiles of the extracts, AEBd-MAO had higher concentrations of total phenolics, total tannins and hydrolysable tannins. The extracts inhibited 100% of the phospholipase and coagulant activity of BaV when pre-incubated. Without pre-incubation, however, there was no reduction in phospholipase activity, although significant inhibition of coagulant activity was observed. In the doses used in folk medicine, without pre-incubation, both extracts inhibited 100% of the coagulant activity of BaV. In vivo, the extracts were unable to inhibit the defibrinating activity of the venom but were effective in inhibiting its edema-inducing activity. In the profiles of the extracts pre-incubated with BaV, not all the protein bands revealed by SDS-PAGE and Western blot were observed. Both extracts had a high antioxidant potential and neither had a cytotoxic effect.

CONCLUSION

Although the concentrations of phenolics in each extract were different, the anti-snakebite potential was similar for the concentrations of extract tested. Our findings are of importance for the quality control of this raw material, which, once tested in accordance with Brazilian National Health Surveillance Agency recommendations, may be suitable for use as a phytomedicine to complement treatment of the local effects induced by Bothrops venoms.

Connarus favosus Planch.: An inhibitor of the hemorrhagic activity of Bothrops atrox venom and a potential antioxidant and antibacterial agent

ETHNOPHARMACOLOGICAL RELEVANCE

The plant species Connarus favosus is used in folk medicine in the west of Pará state, Brazil, to treat snakebites.

AIM OF THE STUDY

To investigate the potential of the aqueous extract of Connarus favosus (AECf) to inhibit hemorrhagic and phospholipase A2 activities induced by Bothrops atrox venom (BaV) and to determine the antioxidant and antimicrobial potentials of the extract.

MATERIALS AND METHODS

AECf was analyzed phytochemically for phenolics (condensed tannins and hydrolyzable tannins) by colorimetry. Antioxidant activity was evaluated by quantitative assays using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Fe(3+)/phenanthroline. Antimicrobial activity was evaluated by the minimal inhibitory concentration test, and cytotoxicity was evaluated using human fibroblast cells (MRC-5). Inhibition of BaV-induced hemorrhagic activity was assessed after oral administration of the extract using pre-treatment, post-treatment and combined (BA plus AECf) treatment protocols. Inhibition of indirect hemolysis caused by phospholipase A2 (PLA2) was investigated in vitro. Interaction between AECf and BaV was investigated by SDS-PAGE electrophoresis, Western blot (Wb) and zymography.

RESULTS

The phytochemical profile of AECf revealed ten secondary metabolite classes, and colorimetry showed high total phenolic and total (condensed and hydrolyzable) tannin content. AECf exhibited high antioxidant and antimicrobial potentials. The IC50 for the cytotoxic effect was 51.91 (46.86-57.50)µg/mL. Inhibition of BaV-induced hemorrhagic activity was significant in all the protocols, and inhibition of PLA2 activity was significant with the two highest concentrations. The BaV/AECf mixture produced the same bands as BaV by itself in SDS-PAGE and Wb although the bands were much fainter. Zymography confirmed the proteolytic activity of BaV, but when the venom was pre-incubated with AECf this activity was blocked.

CONCLUSION

AECf was effective in reducing BaV-induced hemorrhagic activity when administered by the same route as that used in folk medicine and exhibited antioxidant and antimicrobial potentials.

Extracts of Renealmia alpinia (Rottb.) MAAS Protect against Lethality and Systemic Hemorrhage Induced by Bothrops asper Venom: Insights from a Model with Extract Administration before Venom Injection

Renealmia alpinia (Rottb.) MAAS, obtained by micropropagation (in vitro) and wild forms have previously been shown to inhibit some toxic activities of Bothrops asper snake venom if preincubated before injection. In this study, assays were performed in a murine model in which extracts were administered for three days before venom injection. R. alpinia extracts inhibited lethal activity of B. asper venom injected by intraperitoneal route. Median Effective Dose (ED50) values were 36.6 ± 3.2 mg/kg and 31.7 ± 5.4 mg/kg (p > 0.05) for R. alpinia wild and in vitro extracts, respectively. At a dose of 75 mg/kg, both extracts totally inhibited the lethal activity of the venom. Moreover, this dose prolonged survival time of mice receiving a lethal dose of venom by the intravenous route. At 75 mg/kg, both extracts of R. alpinia reduced the extent of venom-induced pulmonary hemorrhage by 48.0% (in vitro extract) and 34.7% (wild extract), in agreement with histological observations of lung tissue. R. alpinia extracts also inhibited hemorrhage in heart and kidneys, as evidenced by a decrease in mg of hemoglobin/g of organ. These results suggest the possibility of using R. alpinia as a prophylactic agent in snakebite, a hypothesis that needs to be further explored.

Inhibition of the toxic effects of Bothrops asper venom by pinostrobin, a flavanone isolated from Renealmia alpinia (Rottb.) MAAS

ETHNOPHARMACOLOGICAL RELEVANCE

Renealmia alpinia has been traditionally used to treat snakebites by indigenous Embera-Katíos tribes belonging to the regions of Antioquia and Chocó, Colombia, and it has been shown to inhibit the enzymatic and biological activities of Bothrops venoms and their purified phospholipase A2 (PLA2) toxins. In addition to its common local usage against snakebites, Renealmia alpinia is commonly used to treat pain. To evaluate the inhibitory ability of pinostrobin, the main compound in the dichloromethane extract of Renealmia alpinia, on the toxic effects of Bothrops asper venom through in vitro and in vivo models and to evaluate its activity against pain and edema.

MATERIALS AND METHODS

Pinostrobin was isolated from the dichloromethane extract of Renealmia alpinia leaves. The protective properties of the extract and of pinostrobin against the indirect hemolytic, coagulant and proteolytic effects of Bothrops asper venom were evaluated in vitro, and the anti-hemorrhagic and anti-inflammatory activity were evaluated in vivo.

RESULTS

Renealmia alpinia extract significantly inhibited the proteolytic activity and indirect hemolytic activity of Bothrops asper venom at a venom:extract ratio of 1:20. Moreover, the present data demonstrate that pinostrobin may mitigate some venom-induced local tissue damage due to hemorrhagic effects, and the compound is also responsible for the analgesic and anti-inflammatory activity of the extract from Renealmia alpinia. This is the first report to describe pinostrobin in the species Renealmia alpinia and its properties in vitro against Bothrops asper venom.

CONCLUSION

Our studies of the activity of Renealmia alpinia against the venom of Bothrops asper have confirmed that this species possesses inhibitory effects against Bothrops asper venom in both in vitro and in vivo models and that these effects may be due to pinostrobin, supporting the traditional usage of the plant. Additionally, pinostrobin may be responsible for the anti-hemorrhagic and analgesic activity (peripheral analgesic activity) of Renealmia alpinia.