Aqueous extract of the bark of Uncaria tomentosa, an amazonian medicinal plant, promotes gastroprotection and accelerates gastric healing in rats

ETHNOPHARMACOLOGICAL IMPORTANCE

Uncaria tomentosa Willd. DC., is used in the Amazonian region of South America, wherein ethnic groups use the plant to treat diseases, including gastric disorders. However, despite its widespread popular use, this species has yet to be assessed for its anti-ulcer effects.

AIM OF THE STUDY

In this study, we aimed to evaluate the in vivo gastroprotective and gastric healing activities of an aqueous extract of the bark of Uncaria tomentosa (AEUt) and sought to gain an understanding of the pharmacological mechanisms underlying these biological effects.

MATERIALS AND METHODS

To verify the gastroprotective properties rats were treated with AEUt (30, 60, or 120 mg/kg) prior to inducing gastric ulceration with ethanol or piroxicam. Additionally, the involvement of nitric oxide, non-protein sulfhydryl compounds (NP-SH), α-2 adrenergic receptors, and prostaglandins was investigated. Furthermore, a pylorus ligature model was employed to investigate the antisecretory activity of AEUt. The gastric healing effects of AEUt (60 mg/kg) were examined in rats in which ulceration had been induced with 80% acetic acid, whereas the quality of healing was evaluated in mice with interleukin-induced recurrent ulcers. We also evaluated the in vivo thickness of the gastric wall using ultrasonography. Moreover, the levels of reduced glutathione (GSH) and malondialdehyde (MDA) were evaluated in ulcerated mucosa, and we determined the activities of the enzymes myeloperoxidase (MPO), N-acetyl-β-D-glycosaminidase, superoxide dismutase, catalase, and glutathione S-transferase. In addition, we assessed the effects of AEUt on cell viability and subjected the AEUt to phytochemical analyses.

RESULTS

Administration of the AEUt (60 or 120 mg/kg) prevented ethanol- and piroxicam-induced ulceration, which was also confirmed histologically. Moreover, we observed that pre-treatment with NEM and indomethacin abolished the gastroprotective effects of AEUt, thereby indicating the involvement of NP-SH and prostaglandins in these protective effects. In addition, we found that the administration of AEUt had no appreciable effects on the volume, acidity, or peptic activity of gastric juice. Furthermore, the AEUt (60 mg/kg) accelerated the gastric healing of acetic acid-induced ulcers by 46.2% and ultrasonographic findings revealed a reduction in the gastric wall thickness in this group. The gastric healing effect of AEUt was also accompanied by a reduction in MPO activity. The AEUt (60 mg/kg) also minimized ulcer recurrence in mice exposed to IL-1β and was associated with the maintenance of GSH levels and a reduction in MDA contents. We deduce that the biological effects of AEUt could be associated with the activities of polyphenols and the alkaloids isomitraphylline and mitraphylline, identified as predominant constituents of the AEUt. Furthermore, we found no evidence to indicate that AEUt would have any cytotoxic effects.

CONCLUSION

Collectively, our findings provide compelling evidence indicating the therapeutic efficacy of U. tomentosa. Our data indicate that compounds in AEUt confer gastroprotection and that this preventive effect of AEUt was accompanied by gastric healing and a reduction in gastric ulcer recurrence. Moreover, we provide evidence to indicate that the gastroprotective and gastric healing effects involve the antioxidant system and anti-inflammatory responses that contribute to preserving the gastric mucosa.

Guillain-Barre syndrome associated to COVID-19 infection: a review of published case reports

INTRODUCTION

The coronavirus disease 2019 (COVID-19) pandemic is a major worldwide health disorder. There is an increasing number of neurological complications recognized with COVID-19 including patients with GBS and its variants.

DEVELOPMENT

A review of the clinical cases of GBS associated to COVID-19 infection published in the last months has been developed. We included 48 patients (31 men, mean age 56.4 years). The most common COVID-19 symptoms were cough (60.4%) and fever (56.3%). Mean time from COVID-19 symptoms to neurologic manifestations was 12.1 days, but in nine patients (18.8%) developed GBS within seven days. Eleven patients (22.9%) presented cranial nerve involvement in the absence of muscle weakness; 36 presented the classic sensory motor variant (75%) and one had a pure motor variant (2.1%). The electrodiagnostic pattern was considered demyelinating in 82.4% of the generalized variants. The presence of hyposmia/dysgeusia was associated with a latency shorter than seven days to GBS onset of symptoms (30% vs 15.6%), and cranial nerve involvement in the absence of weakness (30.8% vs 17.1%). Most patients (87.5%) were treated with intravenous immunoglobulin. Neurological outcome was favorable in 64.6%; 29.2% had respiratory failure and 4.2% died shortly after being admitted.

CONCLUSIONS

GBS in patients with SARS-CoV-2 infection resembles clinically and electrophysiology the classical forms. Further studies are necessary to understand whether GBS frequency is actually increased due to SARS-CoV-2 infection and explore pathogenic mechanisms.

Actividad Antioxidante y Antiproliferativa de Seis Plantas Medicinales del Noroeste de México

Las especies reactivas de oxígeno, que inducen estrés oxidativo en el organismo, son uno de los factores de riesgo para padecer de algún tipo de cáncer. En México los tipos de cáncer con mayor mortalidad son el de próstata, mama, cervicouterino, pulmón e hígado. Los productos naturales representan la forma más antigua de remedios medicinales, para el cáncer esta fuente no es una excepción. En esta investigación, se estudió la actividad antioxidante por ABTS y DPPH, y la actividad antiproliferativa de seis plantas medicinales del noroeste de México. Las cáscaras del fruto de Jacquinia macrocarpa ssp pungens mostraron la mejor actividad antiproliferativa del estudio con una IC50 de 9.2 mg/mL en A549, seguido por B microphylla con IC50 de 13.8 mg/mL en HeLa. Bursera laxiflora obtuvo la mejor actividad antioxidante de las seis plantas frente a los radicales ABTS y DPPH, así como también presentó actividad antiproliferativa en HeLa. La corteza de B. laxiflora contiene compuestos con actividad antioxidante, que probablemente, también sean los mismos que inducen la actividad antiproliferativa en células cancerosas. Por otro lado, J.  macrocarpa y B. microphylla no presentan actividad antioxidante, sin embargo, las tres especies vegetales representan una fuente potencial de moléculas con actividad antiproliferativa.

Gastroprotective activity of hydroalcoholic extract of the leaves of Urera baccifera in rodents

ETHNOPHARMACOLOGICAL IMPORTANCE

The species Urera baccifera (L.) Gaudich. ex Wedd. (Urticaceae) is native to the Americas and is distributed widely throughout Brazil, where it is known as urtiga-brava, urtiga-vermelha, or urtigão. The leaves are often used as anti-inflammatory and antirheumatic agents and for the treatment of gastric disorders. However, the pharmacological mode of action underlying the gastroprotection induced by this species has not been investigated.

AIM OF THE STUDY

To contribute to the knowledge of the gastroprotective mode of action of the hydroalcoholic extract of U. baccifera (HEU) leaves.

MATERIALS AND METHODS

Antiulcerogenic effect of HEU against ethanol-induced acute gastric ulcer was evaluated in rats and mice at doses of 3-300 mg/kg. NO-synthase inhibitor (L-NAME), SH blocker (NEM), cyclooxygenase inhibitor (indomethacin) and alpha 2-adrenergic receptor antagonist yohimbine were used to evaluate the participation of cytoprotective factors in HEU gastroprotection. Moreover, the levels of reduced gluthatione (GSH) and cytokines (TNF, IL-6, IL4 and IL-10), as well as the enzymatic activity of gluthatione S-transferase (GST), myeloperoxidase (MPO), superoxide dismutase (SOD) and catalase (CAT) were measure. Moreover, the samples were analyzed histologically and the antisecretory capability of HEU were quantified using pylorus ligated rats.

RESULTS

The phytochemical analysis of HEU (UPLC/ESI-IT-MS) identified the flavonoids diosmetin and apigenin glucuronide. Furthermore, HEU decreased the occurrence of ethanol-induced ulcers at 30 and 300 mg/kg by 57% and 66%, respectively, compared with the vehicle. The gastroprotective effects were accompanied by increased GSH levels and GST and SOD activity as well as by reduced MPO activity in vivo and in vitro, revealing antioxidant effects and inhibition of neutrophil infiltration. The beneficial effects of 30 and 300 mg/kg HEU were also observed upon histological analyses. Regarding the mode of action, the gastroprotective effect of HEU was abolished by the pre-administration of L-NAME, NEM, indomethacin or yohimbine. Moreover, HEU was able to decrease the IL-6, IL-4 and IL-10 in ulcerated tissue, as well as the pepsin activity of the gastric juice in pylorus-ligated rats.

CONCLUSION

Together, the results confirmed that the gastroprotection elicited by HEU was due reduction in oxidative damage, neutrophil migration, and peptic activity. This work validates the popular use of U. baccifera to treat gastric disorders and supports important future research for the identification of gastroprotective molecules from this species.

The effect of environmentally induced stem temperature gradients on transpiration estimates from the heat balance method in two tropical woody species

Commercially available sap flow gauges were used to evaluate the performance of the stem heat balance (SHB) technique for measuring sap flow in coffee (Coffea arabica L. cv. Yellow Catuai) and koa (Acacia koa Gray) plants under greenhouse and field conditions. Transpiration rates measured gravimetrically and with the SHB technique were similar in greenhouse tests, provided that insulation in addition to that supplied by the gauge manufacturer was applied to reduce radiant heating in the vicinity of the sap flow gauges. Unrealistic estimates of transpiration rates were sometimes obtained under both field and greenhouse conditions as a result of negative stem temperature differentials from below to above the gauge heater, even in the absence of power applied to the heaters. It was possible to correct this environmentally induced bias by means of additional stem insulation that minimized the rate of change in stem temperature, or by applying simple corrections using the DeltaT values for unheated gauges operated as blanks. In the field, where dense canopies reduced the radiant energy load on stems, temperature corrections were unnecessary, because DeltaT values in unheated gauges were near zero.