Luteolin prevents irinotecan-induced intestinal mucositis in mice through antioxidant and anti-inflammatory properties

BACKGROUND AND PURPOSE

Intestinal mucositis refers to mucosal damage caused by cancer treatment, and irinotecan is one of the agents most associated with this condition. Focusing on the development of alternatives to prevent this important adverse effect, we evaluated the activity of the flavonoid luteolin, which has never been tested for this purpose despite its biological potential.

EXPERIMENTAL APPROACH

The effects of luteolin were examined on irinotecan-induced intestinal mucositis in mice. Clinical signs were evaluated. Moreover, histological, oxidative, and inflammatory parameters were analysed, as well as the possible interference of luteolin in the anti-tumour activity of irinotecan.

KEY RESULTS

Luteolin (30 mg·kg^-1 ; p.o. or i.p.) prevented irinotecan-induced intestinal damage by reducing weight loss and diarrhoea score and attenuating the shortening of the duodenum and colon. Histological analysis confirmed that luteolin (p.o.) prevented villous shortening, vacuolization, and apoptosis of cells and preserved mucin production in the duodenum and colon. Moreover, luteolin treatment mitigated irinotecan-induced oxidative stress, by reducing the levels of ROS and LOOH and augmenting endogenous antioxidants, and inflammation by decreasing MPO enzymic activity, TNF, IL-1β, and IL-6 levels and increasing IL-4 and IL-10. Disruption of the tight junctions ZO-1 and occludin was also prevented by luteolin treatment. Importantly, luteolin did not interfere with the anti-tumour activity of irinotecan.

CONCLUSION AND IMPLICATIONS

Luteolin prevents intestinal mucositis induced by irinotecan and therefore could be a potential adjunct in anti-tumour therapy to control this adverse effect, increasing treatment adherence and consequently the chances of cancer remission.

Evidence of gastric ulcer healing activity of Maytenus robusta Reissek: In vitro and in vivo studies

ETHNOPHARMACOLOGICAL RELEVANCE

Maytenus robusta Reissek (Celastraceae) is traditionally used in Brazilian folk medicine to treat gastric ulcer, as a substitute for M. ilicifolia, which is almost extinct. The gastroprotective properties of M. robusta were demonstrated previously using only preventive approaches, such as acute gastric ulcer models. However, the healing effect of M. robusta in gastric ulcers remains unclear.

AIM OF THE STUDY

The current study was carried out to investigate the healing effectiveness of M. robusta hydroalcoholic extract (HEMR) from aerial parts in the acetic acid-induced chronic ulcer model and to determine its effect on cell proliferation, scavenging free radicals, and inflammatory and oxidative damage.

MATERIAL AND METHODS

To evaluate the healing properties of HEMR in vivo, chronic gastric ulcer was induced in rats by 80% acid acetic. Next, different groups of animals (n=6) were treated orally with vehicle (water plus 1% tween, 1 ml/kg), omeprazole (20mg/kg), or HEMR (1-10mg/kg), twice daily for 7 days. At the end of the treatment, the total ulcer area (mm(2)) was measured and a sample of gastric tissue was taken for histological and histochemical analysis. Evaluation of GSH and LOOH levels, GST, SOD, CAT and MPO activity was also performed at the site of the lesion. In parallel, radical scavenging activity, cytoprotective effect, and cell proliferation activity in fibroblasts (L929 cells) were determined by in vitro trials. The antisecretory properties were evaluated using the pylorus ligature model in rats, and the anti-Helicobacter pylori activity was determined in vitro. Acute toxicity was evaluated by relative organ weight and biochemical parameters in serum. The prokinetic properties were also evaluated in mice.

RESULTS

Oral administration of HEMR (10mg/kg) reduced the gastric ulcer area by 53%, compared to the vehicle group (120.0 ± 8.3mm(2)), the regeneration of gastric mucosa was evidenced in histological analysis. Moreover, HEMR treatment increased gastric mucin content and reduced oxidative stress and inflammatory parameters at the site of the ulcer. In vitro, HEMR (1-1000 µg/ml) was able to scavenge free radical DPPH and promote cytoprotection against H2O2 in fibroblasts at 0.1-100 µg/ml. Moreover, HEMR healing properties also were confirmed by enhancement of proliferation and coverage of scratched wounds in fibroblast monolayer. However, HEMR (10mg/kg) by the intraduodenal route did not promote changes in volume, pH, total acidity or pepsin activity in the pylorus ligature model, and HEMR up to 2000 µg/ml also did not present considerable activity against H. pylori. In relation to gastrointestinal motility, HEMR (10mg/kg, p.o) did not provoke alterations. It is also important to mention that oral administration of HEMR did not produce any sign of acute toxicity in animals.

CONCLUSIONS

The data here obtained show that M. robusta has evident ulcer healing potential, mainly through the strengthening of protective factors of gastric mucosa, such as mucus layer, antioxidant defenses and cell proliferation. Taking into account the advantages of cultivation and harvesting of M. robusta compared to M. ilicifolia, and the evidence presented here, it is plausible to conclude that hydroalcoholic extract obtained from aerial parts of M. robusta is an interesting source for the development of a phytotherapeutic formulation to treat gastric ulcer.

Hydroalcoholic extract of Tagetes erecta L. flowers, rich in the carotenoid lutein, attenuates inflammatory cytokine secretion and improves the oxidative stress in an animal model of ulcerative colitis

Given the role of oxidative stress in ulcerative colitis (UC) etiology, and the amount of lutein (a carotenoid with antioxidant properties) in the dry hydroalcoholic extract of Tagetes erecta flowers (DHETE), this study investigated the intestinal anti-inflammatory properties of DHETE in an animal model of UC. The amount of lutein in the extract was determined by ¹H-nuclear magnetic resonance spectroscopy, and total phenols, radical scavenger capability, cytotoxicity, and effects on reactive oxygen species and nitric oxide production were evaluated in vitro. Experimental UC was established by adding 5% dextran sulfate sodium (DSS) to drinking water, with the effects of DHETE (30-300 mg/kg, once a day for 7 days) on the morphological (colon length and weight), clinical (disease activity index and body weight loss), microscopic (histological score and mucin levels), and biochemical parameters analyzed. The lutein concentration found in DHETE was 8.2%, and DHETE scavenged 2,2-diphenyl-1-picrylhydrazyl radicals at 1000 μg/mL The exposure of intestinal epithelial cells to DHETE did not change its viability but reduced reactive oxygen species and nitric oxide production after lipopolysaccharide stimulation. In vivo, DHETE (300 mg/kg) attenuated weight loss, disease activity index, colon shortening, and histopathological changes promoted by DSS intake. Moreover, DHETE increased mucin colonic staining. The treatment with DHETE decreased myeloperoxidase activity as well as tumor necrosis factor and interleukin-6 levels. The extract also increased reduced glutathione levels and catalase activity and normalized superoxide dismutase and glutathione-S-transferase activities. In conclusion, DHETE reduced colitis severity by attenuating inflammatory cytokine secretion and improved the endogenous antioxidant defense in DSS-induced UC in mice.

Polymeric films containing pomegranate peel extract based on PVA/starch/PAA blends for use as wound dressing: In vitro analysis and physicochemical evaluation

Chronic wounds constitute a serious public health problem, and developing pharmaceutical dosage forms to ensure patient comfort and safety, as well as optimizing treatment effectiveness, are of great interest in the pharmaceutical, medical and biomaterial fields. In this work, the preparation of films based on blends of poly(vinyl alcohol), starch and poly(acrylic acid), polymers widely used as pharmaceutical excipients, and pomegranate peel extract (PPE), a bioactive compound with antimicrobial and healing activities relevant to the use as a bioactive wound dressing, was proposed. Initially, the minimum inhibitory concentration (MIC) of the PPE was investigated by an in vitro method. Then, the best concentration of the PPE to be used to prepare the films was researched using an antimicrobial susceptibility test with the disc diffusion method. The microbiological assay was performed in films prepared by the solvent casting method in the presence of two concentrations of PPE: 1.25% w/v and 2.5% w/v. Films containing the lower PPE concentration showed antimicrobial activity against Staphylococcus aureus and Staphylococcus epidermidis, with a difference that was not considered statistically significant when compared to the higher concentration of the extract. Therefore, the films prepared with the lower proportion of PPE (1.25% w/v) were considered for the other studies. The miscibility and stability of the extract in the films were investigated by thermal analysis. Parameters that determine the barrier properties of the films were also investigated by complementary techniques. Finally, in vitro biological tests were performed for safety evaluation and activity research. Analysis of the results showed that the incorporation of the higher proportion of starch in the blend (15% v/v) (PVA:S:PAA:PPE4) yielded smooth, transparent, and domain-free films without phase separation. Additionally, the PVA:S:PAA:PPE4 film presented barrier properties suitable for use as a cover. These films, when subjected to the in vitro hemolytic activity assay, were nonhemolytic and biocompatible. No toxicity from the extract was observed at the concentrations studied. The results of the wound healing in vitro test showed that films containing 1.25% PPE are efficient in reducing the scratch open area, provoking almost total closure of the scratches within 48 h without cytotoxicity.

Artepillin C, drupanin, aromadendrin-4'-O-methyl-ether and kaempferide from Brazilian green propolis promote gastroprotective action by diversified mode of action

ETHOPHARMACOLOGICAL RELEVANCE

The propolis is extensively used in folk medicine in natura or to prepare pharmaceutical formulations since ancient time to improve health or prevent diseases, among them gastrointestinal disorders. Aiming to contribute in the scientific validation about the popular use of Brazilian Green propolis (BGP) against gastritis and gastric ulcer, this work evaluated the antiulcer potential of isolated compounds from BGP, three prenylated p-coumaric acid derivatives and two flavonoids, respectively named: 3,5 diprenyl-4-hydroxycinnamic acid (artepillin C) (1), 3-prenyl-4-dihydroxycinnamoiloxy cinnamic acid (baccharin) (2), 3-prenyl-4-hydroxycinnamic acid (drupanin) (3), aromadendrin-4'-O-methyl-ether (4) and kaempferide (5).

MATERIAL AND METHODS

The compounds were characterized by nuclear magnetic resonance and mass spectrometry. Their gastroprotective effects were evaluated against ethanol/HCl- and indomethacin-induced ulcer in mice. Further, histological, histochemical, oxidative and inflammatory parameters were analyzed at ulcerated tissue. Acid antisecretory activities also were also assessed.

RESULTS

Compound 2 did not reduce the ethanol/HCl- induced ulcer at 30 mg/kg (p.o), whereas the minimum oral gastroprotective doses of 1, 3, 4 and 5 were 0.3, 0.3, 3 and 3 mg/kg, respectively. Besides, these compounds prevented ethanol/HCl-induced ulcer by intraperitoneal route, as well as indomethacin-induced ulcer by oral route. The gastroprotection was accompanied by normalization of superoxide dismutase, catalase and glutathione-S-transferase activities and reduction in myeloperoxidase activity. Moreover, the compounds 4 and 5 increased the gastric mucin content and 1 reduced TNF amount. Furthermore, 1, 3, 4 and 5 decreased volume, pH, total acidity and pepsin activity of the gastric juice from rats.

CONCLUSIONS

Together, our findings showed a diversified mode of action elicited by 1, 3, 4 and 5 on the gastroprotection and contribute to explain the anti-ulcer activity reported for BGP.

Pharmacological reports about gastroprotective effects of methanolic extract from leaves of Solidago chilensis (Brazilian arnica) and its components quercitrin and afzelin in rodents

Solidago chilensis Meyenmost (Asteraceae), popularly known as "Brazilian arnica" or "arnica-do-campo," is widely used in the folk medicine to treat gastric disorders. Based on this, the gastroprotective activity of S. chilensis methanolic extract was investigated. Besides, a phytochemical study allowed isolation of two flavonoids (quercitrin and afzelin). The gastroprotective effects were investigated in acute gastric ulcer models, and the antisecretory activity was assessed in vivo and in vitro. The adhered mucus levels, reduced glutathione (GSH) content and myeloperoxidase (MPO) activity were quantified in ulcerated tissues. The contribution of isolated compounds in extract effects was evaluated, and its doses were calculated according to its yield. To evaluate the in vivo healing properties of S. chilensis methanolic extract, a chronic gastric ulcer was induced in mice by 10 % acetic acid. Evaluation of tumor necrosis factor (TNF) levels was also performed at the site of the acetic acid-induced gastric ulcer. In parallel, effects on cell viability and cell proliferation of fibroblasts (L929 cells) were determined by in vitro trials. Firstly, the S. chilensis methanolic extract (100 or 300 mg/kg) reduced the ulcer area induced by ethanol/HCl in mice when compared to the vehicle group. Moreover, the S. chilensis extract (300 mg/kg) prevented the mucus depletion, the increase in MPO activity and the decrease in the GSH levels in the ulcerated gastric tissue. The S. chilensis extract also was able to decrease the indomethacin-induced gastric ulcer in rats at a dose of 100 mg/kg. The antisecretory effect of the extract (100 mg/kg, intraduodenal (i.d.)) was confirmed by the reduction in the volume and acidity in parallel to an increase in the pH of gastric content. In addition, quercitrin (1.38 mg/kg, but not 0.46 mg/kg) and afzelin (0.026 and 0.078 mg/kg) decreased the ethanol/HCl-induced gastric ulcer. In this model, quercitrin (1.38 mg/kg) prevented the depletion of gastric GSH content and both quercitrin (1.38 mg/kg) and afzelin (0.078 mg/kg) reduced the MPO activity. These compounds also inhibited the H(+),K(+)-ATPase activity at a concentration of 1-100 μg/ml. In addition, the participation of quercitrin and afzelin in these effects also was confirmed. Furthermore, after 4 days of the treatment, an oral administration of S. chilensis methanolic extract (100 mg/kg) reduced the area of the gastric ulcer induced by acetic acid and the regeneration of the gastric mucosa was accompanied by a reduction in gastric TNF levels. The healing properties of the extract also were confirmed by enhancement of proliferation and coverage of scratched wounds in a fibroblast monolayer. Together, our results confirmed the gastroprotective effect of S. chilensis methanolic extract as well as its gastric healing potential and provided some support to the traditional use of S. chilensis for prevention and treatment of gastric lesions in complementation to its known anti-inflammatory properties.

Diuretic and Renal Protective Effect of Kaempferol 3-O-Alpha-l-rhamnoside (Afzelin) in Normotensive and Hypertensive Rats

Our previous study showed that kaempferitrin, the main flavonoid from Bauhinia forficata Link leaves, induces diuresis and saluresis when orally given to rats. Since afzelin (AFZ) and kaempferol (KFL) are active compounds from the biometabolism of kaempferitrin, the diuretic and renal protective properties of these two compounds were evaluated. While the acute treatment with AFZ evoked a diuretic action associated with an increase in Cl^- excretion and a Ca²⁺-sparing effect, KFL did not present any activity. The pretreatment with a muscarinic receptor blocker or with an inhibitor of the cyclooxygenase fully avoided AFZ-induced diuresis. AFZ also induced a prolonged (7-day treatment) diuretic effect in normotensive (NTR) and hypertensive rats (SHR), with an increase of urinary Na⁺ and Cl^- excretion, while it decreased the elimination of Ca²⁺. AFZ was able to decrease ROS and nitrite generation on kidney homogenates in comparison with the SHR group treated with the vehicle, as well as mitigated the changes in the renal corpuscle region (glomerulus and Bowman's capsule). Moreover, AFZ significantly reduced calcium oxalate crystal formation in urine, with inhibition rates of 41% for the NTR and 92% for the SHR group. Taken together, this study shows that AFZ exerts acute and prolonged diuretic effects plus protective renal properties.

Antiulcer mechanisms of Vernonia condensata Baker: A medicinal plant used in the treatment of gastritis and gastric ulcer

ETHNOPHARMACOLOGICAL RELEVANCE

The leaves from Vernonia condensata Baker are broadly used in folk medicine for the treatment of gastric ulcers and dyspepsia. The Brazilian Public Health System (SUS) describes this species as having the potential to serve as a new herbal product with therapeutic benefits.

AIM OF THE STUDY

The purpose of the study was to evaluate the gastroprotective activity and gastric healing properties of a crude ethanolic extract from leaves of V. condensata (CEEV) in different animal models.

MATERIALS AND METHODS

In order to assess the gastroprotective potential of CEEV, ulcer models were established using ethanol and indomethacin. The gastric healing effect was then evaluated in the acetic acid-induced ulcer model, where the tissue was used to assess oxidative levels (reduced glutathione and lipid hydroperoxide levels, as well as superoxide dismutase and catalase activity), inflammatory [myeloperoxidase (MPO)] parameters, and mucin content. Furthermore, the ligature pylorus model, with and without secretagogue stimuli, was employed to investigate the mechanism of action of CEEV. In addition, H(+)K(+)-ATPase activity, MPO activity, and antioxidant activity through the DPPH assay were examined through in vitro trials. Phytochemical analyses were also performed. The ethanol/HCl-induced gastric ulcer method was employed to verify the gastroprotective effect of the main compound in CEEV.

RESULTS

CEEV (30 and 300mg/kg, p.o) exhibited gastroprotective activity and prevented both gastric lesions induced by ethanol or indomethacin in rats. The gastric healing effect of CEEV (300mg/kg, p.o. taken twice a day for a duration of seven days) was confirmed by examining the macroscopic and microscopic appearance of chronic gastric ulcers induced by acetic acid in rats. The restorative effect of CEEV was accompanied by a significant increase in mucin content (PAS staining) and by a reduction in oxidative stress and inflammatory parameters at the site of the ulcer. Moreover, CEEV (300mg/kg), administered via an intraduodenal route, significantly reduced the volume, pH, total acidity and pepsin activity of gastric content in the pylorus ligature model in rats. The gastric acid antisecretory effect of CEEV was maintained even in the presence of cholinergic and gastrinergic, but not histaminergic, stimuli. In vitro, CEEV (1-10µg/ml) was able to scavenge free radical DPPH, but did not promote inhibitory effects on MPO or H(+),K(+)-ATPAse activity. Phytochemical analysis of CEEV indicated that luteolin is the main compound present in the extract. However, luteolin (1, 3 and 10mg/kg, p.o or 1mg/kg, i.p.) did not promote gastroprotection against ethanol/HCl in mice. It is also important to mention that oral administration of CEEV did not produce any sign of acute toxicity in animals.

CONCLUSIONS

V. condensata extract demonstrates gastroprotective effects through the inhibition of gastric secretion via cholinergic and gastrinergic pathways. Furthermore, it exhibits cytoprotective effects, involving antioxidant activity, an increase in mucin content and inhibition of neutrophil migration. Thus, this medicinal plant may be a suitable natural source for the prevention and treatment of gastric lesions.

The effects of baicalein on gastric mucosal ulcerations in mice: Protective pathways and anti-secretory mechanisms

Many flavonoids have been shown to present good results for the treatment of gastric ulcers. Baicalein, a bioactive flavonoid derived from the Scutellaria baicalensis Georgi root, possesses several biological effects, such as anti-inflammatory and antioxidant. This study was conducted to assess the gastroprotective properties of baicalein. Anti-ulcerogenic assay was performed using the protocol of ulcer induced by ethanol/HCl in mice; then, the role of presynaptic α₂-receptors, sulfhydryl (SH) compounds, nitric oxide (NO), prostaglandin (PG) and ATP-sensitive K⁺ (K_ATP) channels in gastroprotection of baicalein was investigated. The levels of reduced glutathione (GSH) and the myeloperoxidase (MPO) activity were measured in the gastric mucosa. Parameters of gastric secretion (volume, [H⁺] and pH) were determined with or without the presence of the secretagogue agent histamine, as well as mucus in gastric contents, by the pylorus ligation model. In vitro H⁺,K⁺-ATPase activity was also determined. Baicalein (10, 30 and 100 mg/kg) exhibited a dose related gastroprotective effect (P < 0.001) against acidified ethanol-induced lesions. The intraperitoneal treatment of mice with a α₂-adrenoreceptor antagonist (yohimbine; 2 mg/kg), a SH compounds blocker (N-ethylmaleimide, NEM; 10 mg/kg), a non-selective inhibitor of NO synthase (N_w-nitro-L-arginine methyl ester hydrochloride, L-NAME; 10 mg/kg), a non-selective inhibitor of cyclo-oxygenase (indomethacin; 10 mg/kg) or a K_ATP channel blocker (glibenclamide; 10 mg/kg) was able to reverse (P < 0.001) the gastroprotective response caused by baicalein (30 mg/kg). Baicalein (30 mg/kg; P < 0.05) was able to increase GSH levels and decreasing MPO activity. The intraduodenal treatment with baicalein (30 and 100 mg/kg) significantly increased (P < 0.05) the gastric mucus secretion. Additionally, the treatment with baicalein reduced (30 and 100 mg/kg; P < 0.05) the secretion volume and total acid secretion, and also increased (10, 30 and 100 mg/kg; P < 0.001) the pH value, after pylorus ligature. Baicalein (30 mg/kg) was also effective in inhibiting the effects of histamine on gastric secretion (volume, [H⁺] and pH; P < 0.001). Baicalein at 10 and 30 μg/mL showed anti-H⁺,K⁺-ATPase activity. In conclusion, the present results provide convincing evidence that baicalein could be used as a cytoprotective (preventive effect) and anti-ulcerogenic (anti-secretory effect) agent in the gastric ulcers.

Diuretic and natriuretic effect of luteolin in normotensive and hypertensive rats: Role of muscarinic acetylcholine receptors

BACKGROUND

Luteolin is a very common phenolic compound found in a wide variety of natural products. Although several biological properties have already been described regarding the beneficial effect of luteolin in the cardiovascular and renal system, no scientific research explored its potential effect as a diuretic agent in experimental trials.

METHODS

Groups of male normotensive (NTR) and spontaneously hypertensive rats (SHR) were orally treated with vehicle, hydrochlorothiazide or luteolin. In another experimental set, in order to verify the possible mechanisms of luteolin-induced diuresis, NTR were treated with vehicle, hydrochlorothiazide, amiloride, L-NAME, indomethacin or atropine, 1h before receiving luteolin. The cumulative urine volume, electrolytes excretion, pH and osmolality were measured at the end of the experiment (after 8h).

RESULTS

Luteolin, at dose of 3mg/kg, was able to induce both diuretic and natriuretic effect in NTR and SHR groups, without interfering with urinary pH, K⁺ or Cl^- levels. While Ca²⁺ content remained unchanged in urine from luteolin-treated group of NTR, luteolin reduced Ca²⁺ excretion in urine from SHR. The treatment with HCTZ and amiloride intensified luteolin-induced diuresis and natriuresis, with an interesting potassium-sparing effect, in addition to an increase in urinary osmolality levels. Moreover, the diuretic and natriuretic action of luteolin was fully avoided in the presence of atropine, a non-selective muscarinic receptor antagonist.

CONCLUSIONS

This study revealed the diuretic and natriuretic effect of luteolin in normotensive and hypertensive rats. Our data also showed the involvement of muscarinic acetylcholine receptors for the renal effects of luteolin.

Natural Agents Modulating ACE-2: A Review of Compounds with Potential against SARS-CoV-2 Infections

One of the biggest challenges of public health worldwide is reducing the number of events and deaths related to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. The angiotensinconverting enzyme 2 (ACE-2), a carboxypeptidase that degrades angiotensin II into angiotensin 1-7, has been identified as a potent receptor for SARS-CoV-2. In the last decades, ACE inhibition has assumed a central role in reducing cardiovascular and renal events. However, with the advent of COVID-19, attention has been turned to ACE-2 as a possible target to reduce virus binding to different human cells. This review aims to discuss recent developments related to the medicinal properties of natural compounds as ACE/ACE-2 inhibitors, which should be highlighted in the future development of studies looking for modulators in SARS-CoV-2 infection. Data show that bioactive compounds isolated from several natural products act by inhibiting ACE/ACE-2, which changes the entire axis of this system. Of the compounds addressed in this review, 7 phenolic compounds, including quercetin, curcumin, naringenin, luteolin, hesperidin, mangiferin, and gallic acid showed binding affinity with molecular ACE-2 target in silico, and 1, esculetin, decreased ACE-2 expression in vivo. Regarding terpenoids and alkaloids, nimbin, withaferin A, andrographolide, zingiberene and, berberine, piperine and thebaine, respectively, showed a binding affinity with molecular ACE-2 target in silico. These findings reinforce the need for future preclinical and clinical studies on these compounds and specific inhibitory effects on ACE-2 of all the other compounds described herein only as nonspecific ACE inhibitors. It is important to mention that some natural compounds such as magnolol, resveratrol, rosmarinic acid, tanshinone IIA, and nicotine have also demonstrated the potential to increase the activity or expression of ACE-2, and could therefore aggravate SARS-CoV-2 infection.

Gastroprotective xanthones isolated from Garcinia achachairu: Study on mucosal defensive factors and H(+), K(+)-ATPase activity

The present study was designed to investigate the gastroprotective effect of xanthones 7-preniljacareubin (PJB), 1,3,5,6-tetrahydroxy xanthone (THX), 3-demethyl-2-geranyl-4-prenylbellidypholine (DGP) and 1,5,8-trihydroxy-4', 5'-dimethyl-2H-pyrane (2,3:3,2)-4-(3-methylbut-2-enyl) xanthone (TDP) isolated of branches from G. achachairu. Their structures were identified through the spectroscopic analysis in comparison with previously reported data. The xanthones were tested at dose of 10 mg/kg against ethanol 60%/HCl 0.3 N-induced gastric ulcer in female swiss mice. The xanthones PJB, THX, DGP and TDP exhibit gastroprotective effect after intraperitoneal treatment, but only the first two displayed anti-ulcer activity after oral administration. Both PJB and THX augmented the antioxidative capacity of tissue by an increase in glutathione levels, as well as were able to prevent an increase in myeloperoxidase activity and tumor necrosis factor level. On the other hand, only THX showed an in vitro free radical scavenger activity, and only PJB avoided mucus depletion on gastric mucosa, which was not associated with an increase in mucin production at glandular level. In addition, PJB and THX inhibited the in vitro H(+)K(+)-ATPase activity at similar range as omeprazole. Together, these results demonstrate the anti-ulcer efficacy of xanthones isolated from G. achachairu, which can contribute for future directions in the development of effective strategies to improve gastric diseases.

Role of the antioxidant properties in the gastroprotective and gastric healing activity promoted by Brazilian green propolis and the healing efficacy of Artepillin C

Green propolis is a resinous substance used in folk medicine given its anti-inflammatory, antibacterial, and anti-ulcer effects. Our research group has already confirmed the gastroprotective activity of hydroalcoholic extract from green propolis (HEGP), as well as of its main isolated compounds. In continuity, this study evaluated the antioxidant mode of action involved in the preventive effect induced by HEGP, and its therapeutic gastric healing potential on installed ulcers. In addition, the healing effect of its main compound Artepillin C was also investigated. Acute and chronic ulcers were induced in rats by given ethanol or acetic acid, respectively. In acute model, the rats were orally pre-treated with vehicle (water plus 1% Tween, 1 mL/kg), HEGP (30-300 mg/kg), or carbenoxolone (200 mg/kg) 1 h prior the ulcer induction. In the chronic ulcer protocol, the rats received vehicle (water plus 1% Tween, 1 mL/kg), HEGP (300 mg/kg), or omeprazole (20 mg/kg) twice a day by 7 days, whereas groups of mice received vehicle (water plus 1% Tween, 1 mL/kg), Artepillin C (18 mg/kg), or ranitidine (20 mg/kg) twice a day by 4 days. Ulcerated tissue was collected for histological, histochemical, immunostaining, oxidative, and inflammatory analyses. The in vitro scavenger activity of HEGP was also verified using the DPPH assay. The oral pre-treatment with HEGP (100 and 300 mg/kg) prevented the gastric epithelial damage promoted by ethanol. Besides, HEGP (100 and 300 mg/kg) reduced SOD activity about 11% and 26%, respectively, and increased the activity of GST around 20% and CAT in 80%. HEGP (300 mg/kg) also reduced the production of reactive oxygen species, as well as lipoperoxidation levels in the ethanol-ulcerated tissue. In the acetic acid-induced chronic ulcer, the daily treatment with HEGP (300 mg/kg) accelerates the healing process by 71%. In this model, HEGP normalized SOD and CAT activity and increased GST activity by 109% when compared to non-ulcerated rats. In both models, the extract administration increased the mucin PAS staining and reduced the myeloperoxidase activity at the ulcer site. Moreover, the treatment with HEGP enhanced the PCNA immunostaining, but did not alter the concentration of collagen in the acetic acid-ulcerated tissue. The extract had a direct DPPH radical-scavenging ability (LogIC₅₀: 0.56). Besides, as expected, HPLC analysis showed Artepillin C as a major compound and its administration at 18 mg/kg also accelerated the gastric healing ulcer process in mice. Our findings confirm that HEGP displays both gastroprotective and gastric healing properties, contributing to the validation of its popular use as preventive and therapeutic approaches. These actions occur through the increase in mucin production and the reestablishment of the oxidative balance due to a reduction in gastric inflammation.

Gastroprotective and anti-secretory mechanisms of 2-phenylquinoline, an alkaloid isolated from Galipea longiflora

BACKGROUND

We previously described the gastroprotective effect of 2-phenylquinoline (2-PQ), the main alkaloid isolated from the bark of Galipea longiflora (Rutaceae). However, despite the significant and promising results, the pharmacological mechanisms of the gastroprotection induced by 2-PQ have not been investigated.

PURPOSE

To evaluate the mechanisms underlying the gastroprotective effects of 2-PQ.

STUDY DESIGN

We used an in vivo mouse ulcer model and in vitro methodologies involving H⁺/K⁺-ATPase and L929 murine fibroblasts.

METHODS

The gastroprotective activity of 2-PQ (10-100 mg/kg, orally, p.o) was assessed against gastric ulcer induced by 60% ethanol/0.03 M hydrochloric acid (HCl) in mice or that induced by indomethacin (80 mg/kg, p.o) in rats. The cytotoxicity was assessed in L929 murine fibroblasts. Ulcerated tissues were analyzed histologically, histochemically, and biochemically. The antisecretory activity of 2-PQ was evaluated in vivo and in vitro.

RESULTS

2-PQ showed no cytotoxicity, reduced the lesion area induced by ethanol/HCl (log half-maximal effective dose, ED₅₀ = 1.507), and the histological evaluation supported these results. Furthermore, 2-PQ reduced indomethacin-induced gastric ulceration. The gastroprotection was accompanied by normalization of superoxide dismutase (SOD) and glutathione-S-transferase (GST) activity, an intense increase in reduced glutathione (GSH) levels, and reduction in lipid peroxide (LPO) and tumor necrosis factor (TNF)-α levels in the gastric mucosa. The antisecretory properties of 2-PQ were confirmed by the decreased volume and total acidity of the gastric juice, and it reduced histamine- or pentagastrin-stimulated gastric acid secretion. However, 2-PQ did not change the in vitro H⁺/K⁺-ATPase activity or the content of gastric-adhered mucous in mice. In addition, pretreatment with N-ethylmaleimide, NG-nitro-l-arginine methyl esters, yohimbine, or indomethacin reversed the gastroprotective effect of 2-PQ, suggesting nitric oxide, nonprotein sulfhydryl compounds, α-2-receptors, and prostaglandin were involved.

CONCLUSION

2-PQ provides gastroprotection by reducing oxidative damage and inhibiting acid secretion mediated by histaminergic and gastrinergic regulatory pathways.

Gallic acid, a phenolic compound isolated from Mimosa bimucronata (DC.) Kuntze leaves, induces diuresis and saluresis in rats

Although present in the leaves of Mimosa bimucronata (DC.) and many other medicinal plants commonly used to augment urinary volume excretion, the effects of gallic acid as a diuretic agent remain to be studied. Wistar rats were orally treated with vehicle, hydrochlorothiazide, or gallic acid. The effects of gallic acid in the presence of hydrochlorothiazide, furosemide, amiloride, L-NAME, atropine, and indomethacin were also investigated. Diuretic index, pH, conductivity, and electrolyte excretion were evaluated at the end of the experiment (after 8 or 24 h). Gallic acid induced diuretic and saluretic (Na⁺ and Cl^-) effects, without interfering with K⁺ excretion, when orally given to female and male rats at a dose of 3 mg/kg. These effects were associated with increased creatinine and conductivity values while pH was unaffected by any of the treatments. Plasma Na⁺, K⁺, and Cl^- levels were not affected by any of the acute treatments. The combination with hydrochlorothiazide or furosemide was unable to intensify the effects of gallic acid when compared with the response obtained with each drug alone. On the other hand, the treatment with amiloride plus gallic acid amplified both diuresis and saluresis, besides to a marked potassium-sparing effect. Its diuretic action was significantly prevented in the presence of indomethacin, a cyclooxygenase inhibitor, but not with the pretreatments with L-NAME or atropine. Although several biological activities have already been described for gallic acid, this is the first study demonstrating its potential as a diuretic agent.

Usnic acid enantiomers restore cognitive deficits and neurochemical alterations induced by Aβ1-42 in mice

Alzheimer's disease (AD) is the most prevalent form of dementia with a complex pathophysiology not fully elucidated but with limited pharmacological treatment. The Usnic acid (UA) is a lichen secondary metabolite found in two enantiomeric forms: (R)-(+)-UA or (S)-(-)-UA, with antioxidant and anti-inflammatory potential. Thus, given the role of neuroinflammation and oxidative injury in the AD, this study aimed to investigate experimentally the cognitive enhancing and anti-neuroinflammatory effects of UA enantiomers. First, the interactions of UA on acetylcholinesterase (AChE) was assessed by molecular docking and its inhibitory capability on AChE was assessed in vitro. In vivo trials investigated the effects of UA enantiomers in mice exposed to Aβ_1-42 peptide (400 pmol/mice) intracerebroventricularly (i.c.v.). For this, mice were treated orally during 24 days with (R)-(+)-UA or (S)-(-)-UA at 25, 50, or 100 mg/kg, vehicle, or donepezil (2 mg/kg). Animals were submitted to the novel object recognized, Morris water maze, and inhibitory-avoidance task to assess the cognitive deficits. Additionally, UA antioxidant capacity and neuroinflammatory biomarkers were measured at the cortex and hippocampus from mice. Our results indicated that UA enantiomers evoked complex-receptor interaction with AChE like galantamine in silico. Also, UA enantiomers improved the learning and memory of the animals and in parallel decreased the myeloperoxidase activity and the lipid hydroperoxides (LOOH) on the cortex and hippocampus and reduced the IL-1β levels on the hippocampus. In summary, UA restored the cognitive deficits, as well as the signs of LOOH and neuroinflammation induced by Aβ1-42 administration in mice.

Hydroalcoholic extract from Baccharis dracunculifolia recovers the gastric ulcerated tissue, and p-coumaric acid is a pivotal bioactive compound to this action

Baccharis dracunculifolia is a medicinal plant native to southeastern Brazil and is the main botanical source used by bees (Apis mellifera) in the manufacture of green propolis and display similar gastroprotective action and chemical profile. This article reports the healing gastric ulcer activity of the hydroethanolic extract of B. dracunculifolia (HEBD) in an acetic acid-induced ulcer model. In addition to the extract, the isolated compounds ferulic acid, p-coumaric acid, caffeic acid, baccharin, and aromadendrin-4'-O-methyl ether were also assayed. HEBD at a dose of 300 mg/kg reduced the ulcerated area by 49.4% after treatment for 7 days, twice a day. Histological analyses revealed that the margins and base of the ulcer obtained significant regeneration, and periodic acid Schiff base staining showed a 78.2% increase in the mucin levels. The action on the enzymatic antioxidant system demonstrated an increased activity of superoxide dismutase and glutathione-S-transferase, in addition to raising glutathione reduced levels and myeloperoxidase activity. HEBD did not show cytotoxicity in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylterazole bromine test. In vitro, HEBD inhibited the H⁺ /K⁺ -ATPase enzyme and showed antioxidant activity in the 2,2 diphenyl-1-picryllydrazyl test. Regarding the isolated compounds, oral administration of p-coumaric acid (15 mg/kg) reduced the ulcerated area by 66.2%. The results suggest that HEBD recovers the gastric ulcerated tissue, raising mucus and antioxidant enzyme levels, and reducing the H⁺ /K⁺ -ATPase activity. In addition, the findings confirm that p-coumaric acid is a pivotal bioactive compound on the gastric healing effects elicited by HEBD. © 2019 BioFactors, 45(3):479-489, 2019.

Constituents of leaves from Bauhinia curvula Benth. exert gastroprotective activity in rodents: role of quercitrin and kaempferol

The Bauhinia genus is known as "Pata-de-Vaca" and a wide variety of these species are used in Brazilian folk medicine due to their gastroprotective properties. This study aimed to investigate the antiulcer efficacy of the hydroalcoholic extract from B. curvula (HEBC) leaves, as well as its semi-purified fraction (SPFr) and the contribution of their phytochemicals constituents for this effect. For that, ethanol 60%/HCl 0.3 M- and indomethacin-induced gastric ulcer were performed in rodents. Gastric ulcerated tissues were processed for histological, histochemical and biochemical analysis. The oral treatment with HEBC and SPFr decreased the gastric ulcer induced by ethanol/HCl in mice and by indomethacin (only HEBC) in rats. The gastroprotective effect of HEBC was abolished in mice pretreated with Nω-Nitro-L-arginine methyl ester, N-Ethylmaleimide, glibenclamide or indomethacin. Both HEBC and SPFr reduced myeloperoxidase activity in parallel with a decrease of lipoperoxides content at the site of the lesion. On the other hand, HEBC did not alter volume, pH, total acidity or pepsin activity of acid gastric secretion in rats, and neither inhibited the in vitro H(+),K(+)-ATPase activity. Additionally, the compounds identified and isolated from the SPFr, the flavonoids quercitrin (65%) and kaempferol (35%), were able to diminish the extent of ulcerated area induced by both ethanol/HCl and indomethacin. Taking together, these findings show that B. curvula extracts present gastroprotective effect, mainly explained by the presence of flavonoids quercitrin and kaempferol, which may possibly improve the defensive factors of gastric mucosa.

Gastroprotective effect of the alkaloid boldine: Involvement of non-protein sulfhydryl groups, prostanoids and reduction on oxidative stress

Boldine is the main alkaloid of Peumus boldus Molina, widely used in the traditional medicine for the treatment of digestive disorders. It is a compound with excellent antioxidant and anti-inflammatory properties already described. Despite the widespread use of P. boldus for digestive disorders treatment, the gastroprotective effect of Boldine remains unknown. Considering the need for new approaches to treat gastric ulcers with fewer side effects than current therapy, this study aimed to investigate the gastroprotective effect of Boldine in mice, as well as the mechanisms underlying this effect. The gastroprotective effect of Boldine was evaluated on gastric ulcer induced by 60% ethanol/0.3 M HCl or indomethacin (100 mg/kg) in mice. Histological analysis and the mucin-like glycoprotein content were evaluated in ethanol-ulcerated tissue, as well as, oxidative stress and inflammatory parameters. The mechanisms involved in the effect of Boldine were evaluated by pretreating mice with NEM (a sulfhydryl group chelator, 10 mg/kg, i.p.), l-NAME (a non-selective nitric oxide synthase inhibitor, 70 mg/kg, i.p.), yohimbine (an alpha-adrenergic receptor antagonist, 2 mg/kg, i.p.) and indomethacin (a cyclooxygenase inhibitor, 10 mg/kg, i.p.). In addition, the in vitro effect of Boldine on H⁺/K⁺-ATPase activity was determined. Boldine was able to protect gastric mucosa against the damage induced by ethanol/HCl and indomethacin, as evidenced by reduced lesion area and histological analysis. Moreover, the alkaloid reduced oxidative stress and inflammatory mediators in ethanol-ulcerated tissue, beyond has increased mucin-like glycoprotein amount. Finally, Boldine effect is dependent on non-protein sulfhydryl groups and prostanoids but does not involve the inhibition of H+/K + -ATPase activity, being a promising natural resource for gastric ulcer treatment.