Purification, Characterization, and Assessment of Antimicrobial Activity and Toxicity of Portulaca elatior Leaf Lectin (PeLL)

Lectins are carbohydrate-binding proteins with several bioactivities, including antimicrobial properties. Portulaca elatior is a species found at Brazilian Caatinga and data on the biochemical composition of this plant are scarce. The present work describes the purification of P. elatior leaf lectin (PeLL) as well as the assessment of its antimicrobial activity and toxicity. PeLL, isolated by chromatography on a chitin column, had native liquid charge and subunit composition evaluated by electrophoresis. Hemagglutinating activity (HA) of PeLL was determined in the presence of carbohydrates or divalent cations, as well as after heating and incubation at different pH values. Changes in the lectin conformation were monitored by evaluating intrinsic tryptophan fluorescence and using the extrinsic probe bis-ANS. Antimicrobial activity was evaluated against Pectobacterium strains and Candida species. The minimal inhibitory (MIC), bactericidal (MBC), and fungicidal (MFC) concentrations were determined. Finally, PeLL was evaluated for in vitro hemolytic activity in human erythrocytes and in vivo acute toxicity in mice (5 and 10 mg/kg b.w. per os). PeLL (pI 5.4; 20 kDa) had its HA was inhibited by mannose, galactose, Ca²⁺, Mg²⁺, and Mn²⁺. PeLL HA was resistant to heating at 100 °C, although conformational changes were detected. PeLL was more active in the acidic pH range, in which no conformational changes were observed. The lectin presented MIC and MBC of 0.185 and 0.74 μg/mL for all Pectobacterium strains, respectively; MIC of 1.48 μg/mL for C. albicans, C. tropicalis, and C. krusei; MIC and MFC of 0.74 and 2.96 μg/mL for C. parapsilosis. No hemolytic activity or signs of acute toxicity were observed in the mice. In conclusion, a new, low-toxic, and thermostable lectin was isolated from P. elatior leaves, being the first plant compound to show antibacterial activity against Pectobacterium.

Saline extract of Portulaca elatior leaves with photoprotective and antioxidant activities does not show acute oral and dermal toxicity in mice

The present study aimed to evaluate saline extracts from the leaves (LE) and stem (SE) of Portulaca elatior in relation to their phytochemical composition and photoprotective and antioxidant effects, as well as to evaluate the toxicity of the leaf extract. The extracts were characterized for protein concentration and phenol and flavonoid contents, as well as for thin layer chromatography (TLC) and high-performance liquid chromatography (HPLC) profiles. Total antioxidant capacity and DPPH and ABTS+ scavenging activities were determined. In the photoprotective activity assay, the sun protection factor (SPF) was calculated. The toxicity evaluation of LE included in vitro hemolytic assay and in vivo oral and dermal acute toxicity assays in Swiss mice. LE showed the highest protein, phenol, and flavonoid (8.79 mg/mL, 323.46 mg GAE/g, and 101.96 QE/g, respectively). TLC revealed the presence of flavonoids, reducing sugars, terpenes, and steroids in both extracts. In HPLC profiles, LE contained flavonoids, while SE contained flavonoids and ellagic tannins. The antioxidant activity assays showed the lowest IC50 values ​(34.15-413.3 µg/mL) for LE, which presented relevant SPF (> 6) at 50 and 100 µg/mL. LE demonstrated low hemolytic capacity, and no signs of intoxication were observed in mice treated orally or topically at 1000 mg/kg. However, at 2000 mg/kg, an increase in the mean corpuscular volume of erythrocytes and a reduction in lymphocytes were observed; animals treated topically with 2000 mg/kg displayed scratching behavior during the first hour of observation and showed edema and erythema that regressed after six days. In conclusion, LE did not present acute oral or dermal toxicity in Swiss mice at a dose of 1000 mg/kg and showed slight toxicity in animals treated with 2000 mg/kg.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43188-022-00160-2.

Antinociceptive and Anti-Inflammatory Effects of Saline Extract and Lectin-Rich Fraction from Microgramma vacciniifolia Rhizome in Mice

Previous studies have characterized a saline extract from Microgramma vacciniifolia rhizome and its lectin (MvRL)-rich fraction with low acute toxicity. In the present study, we evaluated these preparations for acute toxicity (1,000 mg/kg) and antinociceptive and anti-inflammatory activities (100-400 mg/kg for the extract and 25-50 mg/kg for the fraction). No signs of toxicity were observed. Both the extract and fraction increased the latency period for nociception in the hot plate assay, decreased writhing induced by acetic acid, and promoted analgesic effects in phases 1 and 2 of the formalin test. The antinociceptive mechanism was attributed to interactions with opioid receptors and K⁺ ATPase channels. The extract and fraction decreased carrageenan-induced paw edema in 46.15 % and 77.22 %, respectively, at the highest doses evaluated. Furthermore, the fraction was shown to act on the bradykinin pathway. The ability to decrease leukocyte migration after treatment was also verified in the peritonitis and air pouch models. In exudates collected from air pouches, decreased tumor necrosis factor (TNF)-α and increased interleukin (IL)-10 levels were noted. Both the extract and fraction also effectively inhibited the development of granulomatous tissue. In conclusion, the substances investigated in this study can be used for the development of novel therapeutic options for pain and inflammatory processes.

Pilosocereus gounellei (Cactaceae) stem extract decreases insulin resistance, inflammation, oxidative stress, and cardio-metabolic risk in diet-induced obese mice

ETHNOPHARMACOLOGICAL RELEVANCE

Pilosocereus gounellei (xique-xique) is a popular cactus from Caatinga, traditionally used to counter inflammatory processes and indicated as a hypoglycemic agent. Previous studies have shown that mice treated orally with saline extract of P. gounellei stem (containing flavonoids and sugars) showed decreased serum lipid levels.

AIM OF THE STUDY

In this work, we evaluated whether this extract would have beneficial effects against hyperglycemia and inflammatory status related to obesity in mice fed a high-fat diet (HFD).

METHODS

Obese animals were treated daily per os with the extract (EXT; 125, 250, and 500 mg/kg), metformin (MET; 400 mg/kg), or saline solution (diet-induced obese, DIO) for 21 days. A group of non-obese animals served as the control. We evaluated lipid profile, glucose and insulin tolerance, atherogenic indices, histological alterations, cytokine levels, and oxidative stress in liver, muscle, and adipose tissue.

RESULTS

At the end of the experiment, mice from EXT groups showed lower body weight and total cholesterol, LDL-cholesterol, and triglycerides compared with the DIO group; in addition, HDL-cholesterol levels and glucose and insulin tolerance were similar to those of the control group. When compared with the DIO group, the extract-treated mice showed reduction in cardiac risk ratio, atherogenic coefficient, atherogenic index of plasma, and Castelli's Risk Index II; decrease in epididymal fat; reduction in steatosis, collagen deposition, and liver inflammation; lower serum levels of pro-inflammatory cytokines (tumor necrosis factor α, interleukin 6, and monocyte chemoattractant protein-1); inhibited lipid peroxidation; and increased superoxide dismutase levels in liver, muscle, and adipose tissue.

CONCLUSION

The P. gounellei saline extract was able to improve physiological parameters of obese mice, which highlight the potential of this plant as source of compounds with biotechnological relevance for pharmaceutical industry.

Genotoxicity assessment of saline extract from Pilosocereus gounellei (Cactaceae) and its chemopreventive effect against cyclophosphamide-induced DNA damage

Pilosocereus gounellei (Cactaceae) is used to treat wounds and inflammation. In this study, we evaluated whether the saline extract from its stem would have genotoxic or anti-genotoxic effects. In the genotoxicity evaluation, mice received the extract (500, 1,000, or 2,000 mg/kg) orally while negative and positive controls were treated with saline solution (0.9% NaCl) per os and cyclophosphamide (CPA, 80 mg/kg i.p.), respectively. In the anti-genotoxicity assay, using other animals, treatments were carried out by administering the extract (500, 1,000 or 2,000 mg/kg) or saline solution (negative control) per os and then CPA (80 mg/kg i.p.) 1 h later. Genotoxic effects were evaluated by micronucleus test and comet assay using peripheral blood and bone marrow cells. Oral administration of only the extract at 500 and 1,000 mg/kg did not result in genotoxicity. A slight increase in the incidence of micronucleus was observed at the highest dose (2,000 mg/kg). Administration of the extract before CPA reduced the micronucleated polychromatic erythrocytes (MNPCE) number by 49.07–71.43%, and DNA fragmentation in peripheral blood (85.04–94.44%) and bone marrow (87.43–92.70%) cells also decreased. In conclusion, when administered orally at the tested doses, the extract is genotoxically safe, being cautious in doses above 1,000 mg/kg, and has a protective effect against CPA-induced DNA damage.