Mohamad Fawzi Mahomoodally

Antioxidant and anti–glycation activities correlates with phenolic composition of tropical medicinal herbs

OBJECTIVE To determine the contribution of total phenolic content (TPC) in glycation inhibitory activity of common tropical medicinal food and spices with potential antioxidative properties. METHODS In vitro glucose-bovine serum albumin (BSA) assay was used. Ethanolic extracts of ten common household condiments/herbs (Allium sativum, Zingiber officinale, Thymus vulgaris, Petroselinum crispum, Murraya koenigii Spreng, Mentha piperita L., Curcuma longa L., Allium cepa L., Allium fistulosum and Coriandrum sativum L.) were evaluated for antioxidative activity by 2,2-diphenyl-2-picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP) and the TPC, flavonoid and tannins content were determined. RESULTS Findings showed good correlation between TPC/DPPH (r = 0.8), TPC/FRAP (r = 0.8), TPC/anti-glycation (r = 0.9), DPPH/anti-glycation (r = 0.6), FRAP/anti-glycation (r = 0.9), Flavonoid/anti-glycation (r = 0.7) and Tannins/anti-glycation (r = 0.8) and relatively fair correlation for TPC/Flavonoids (r = 0.5) and TPC/Tannins (r = 0.5). Results imply that these plants are potential sources of natural antioxidants which have free radical scavenging activity and might be used for reducing oxidative stress. CONCLUSIONS The positive glycation inhibitory and antioxidative activities of these tropical herbs suggest a possible role in targeting ageing, diabetic complications and oxidative stress related diseases.

Antimicrobial Activities and Phytochemical Profiles of Endemic Medicinal Plants of Mauritius

Abstract Medicinal plants are assuming widespread use in the primary health care of individuals and communities. In the current study, we investigated the antimicrobial activities of two endemic plants, Antidesma madagascariense. Lam. and Erythroxylum macrocarpum. O. E. Schulz, which form part of the local pharmacopoeia of Mauritius. Aqueous and methanol extracts of the leaves and twigs of both plants were tested in vitro. against three Gram-negative and five Gram-positive strains of bacteria, including a resistant strain of bacteria. Moreover, they were subjected to antifungal assays against Candida albicans. ATCC 10231 and Aspergillus niger. ATCC 16404, a human and a plant pathogenic microorganism, respectively, known to be good indicators of antifungal activity. It was found that aqueous extracts of both plants possess broad-spectrum antibacterial properties against the test organisms compared to methanol extracts, which gave poor inhibition zones. Moreover, the antibacterial substance within these plants seemed to be most prominent in the leaves and least in the twigs, and the best inhibitory activity was observed for Gram-positive bacteria (Staphylococcus aureus. ATCC 25923). Aqueous extracts of both plants do not possess antifungal properties except the methanol extract against A. niger.. Phytochemical screening of the plants showed the presence of at least tannins, phenols, flavonoids, and alkaloids, which are known antimicorbial compounds. In conclusion, the observed antimicrobial properties would tend to further validate the medicinal properties of these commonly used endemic medicinal plants in Mauritius.

Screening for Alternative Antibiotics: An Investigation into the Antimicrobial Activities of Medicinal Food Plants of Mauritius

The present study was designed to evaluate the antimicrobial activities of 2 endemic medicinal plants; Faujasiopsis flexuosa (Asteraceae) (FF) and Pittosporum senacia (Pittosporaceae) (PS) and 2 exotic medicinal plants, Momordica charantia (Cucurbitaceae) (MC) and Ocimum tenuiflorum (Lamiaceae) (OT) that forms part of local pharmacopoeia of Mauritius and correlate any observed activity with its phytochemical profile. Aqueous and organic fractions of the leaves, fruits, and seeds of these plants were subjected to antimicrobial testing by the disc diffusion method against 8 clinical isolates of bacteria and 2 strains of fungus. It was found that MC, OT, and FF possessed antimicrobial properties against the test organisms. The MIC for MC ranged from 0.5 to 9 mg/mL and that of FF from 2 to 10 mg/mL and the lowest MIC value (0.5 mg/mL) was recorded for the unripe fruits of MC against E. coli. On the other hand, higher concentration of the unripe MC fruit extract of 9 mg/mL was needed to be effective against a resistant strain of Staphylococcus aureus (MRSA). The antimicrobial effect against MRSA was lost upon ripening of the fruits. The methanolic extract of both MC and FF showed highest MIC values compared to the corresponding aqueous extract, which indicates the low efficacy and the need of higher doses of the plant extract. Phytochemical screening of the plants showed the presence of at least tannins, phenols, flavonoids, and alkaloids, which are known antimicrobial phyto-compounds. In conclusion, the observed antimicrobial properties would tend to further validate the medicinal properties of these commonly used endemic medicinal and food plants of Mauritius.

Relationship Between Total Phenolic Content, Antioxidant Potential, and Antiglycation Abilities of Common Culinary Herbs and Spices

Advanced glycation endproducts and oxidative stress contribute to the pathogenesis of diabetic complications. The total phenolic content (TPC), antioxidant, and antiglycation properties of crude ethanolic extracts of 10 common culinary herbs and spices from Mauritius were investigated in vitro. Fluorescence at 370 nm/440 nm was used as an index of albumin glycation. Allium sativum had the highest TPC (3.1 mg GAE/mL), whereas Allium cepa L. showed the highest radical scavenging capacity (72%) and Zingiber officinale had the most potent ferric-reducing antioxidant power (FRAP; 2.99 mg AAE/mL). In contrast, Thymus vulgaris and Petroselinum crispum had the most potent antiglycation activity with IC(50) values of 21.8 and 200 mg/mL, respectively. There was no significant correlation between TPC (r=0.001), FRAP (r=0.161), and the antiglycation activity (r=0.034) for the extracts studied. Therefore, the results showed that antiglycation properties of plant-derived extracts cannot always be attributed to their phenolic content or antioxidant potential.

In vitro and in silico Studies of Mangiferin from Aphloia theiformis on Key Enzymes Linked to Diabetes Type 2 and Associated Complications

BACKGROUND Mangiferin, was identified in the crude methanol extract, ethyl acetate, and n-butanol fractions of Aphloia theiformis (Vahl.) Benn. OBJECTIVE This study aimed to analyze the plausible binding modes of mangiferin to key enzymes linked to diabetes type 2 (DT2), obesity, hypertension, Alzheimers disease, and urolithiasis using molecular docking. METHOD Crystallographic structures of α-amylase, α-glucosidase, glycogen phosphorylase (GP), pancreatic lipase, cholesterol esterase (CEase), angiotensin-I-converting enzyme (ACE), acetyl cholinesterase (AChE), and urease available on the Protein Databank database were docked to mangiferin using Gold 6.0 software. RESULTS We showed that mangiferin bound to all enzymes by π-π and hydrogen bonds mostly. Mangiferin was docked to both allosteric and orthosteric sites of α-glucosidase by π-π interactions. However, several hydrogen bonds were observed at the orthosteric position, suggesting a preference for this site. The docking of mangiferin on AChE with the catalytic pocket occupied by paraoxon could be attributed to π-π stacking involving amino acid residues, Trp341 and Trp124. CONCLUSION This study provided an insight of the molecular interaction of mangiferin with the studied enzymes and can be considered as a valuable tool for designing new drugs for better management of these diseases.

Multiple pharmacological targets, cytotoxicity, and phytochemical profile of Aphloia theiformis (Vahl.) Benn.

Aphloia theiformis (Vahl.) Benn. (AT) is traditionally used in Sub-Saharan African countries including Mauritius as a biomedicine for the management of several diseases. However, there is a dearth of experimental studies to validate these claims. We endeavoured to evaluate the inhibitory effects of crude aqueous extract as traditionally used together with the crude methanol extracts of AT leaves on urease, angiotensin (I) converting enzyme (ACE), acetylcholinesterase (AChE), cholesterol esterase (CEase), glycogen phosphorylase a (GPa), and glycation in vitro. The crude extract showing potent activity against the studied enzymes was further partitioned using different solvents of increasing polarity. The enzyme inhibitory and antiglycation activities of each fraction was assessed. Kinetic of inhibition of the active crude extract/fractions on the aforementioned enzymes was consequently determined using Lineweaver-Burk plots. An ultra-high performance liquid chromatography (UHPLC-UV/MS) system was used to establish the phytochemical profile of AT. The real time cell analysis system (iCELLigence™) was used to monitor any cellular cytotoxicity of AT. Crude methanolextract (CME) was a potent inhibitor of the studied enzymes, with IC50 ranging from 696.22 to 19.73μg/mL. CME (82.5%) significantly (p<0.05) inhibited glycation and was comparable to aminoguanidine (81.5%). Ethyl acetate and n-butanol fractions of CME showed non-competitive, competitive, and uncompetitive mode of inhibition against ACE, CEase, and AChE respectively. Mangiferin, a xanthone glucoside was present in CME, ethyl acetate, and n-butanol fractions. Active extract/fractions were found to be non-cytotoxic (IC50>20μg/mL) according to the U.S National Cancer Institute plant screening program. This study has established baseline data that tend to justify the traditional use of AT and open new avenues for future biomedicine development.

Experimental evidence for in vitro fluid transport in the presence of a traditional medicinal fruit extract across rat everted intestinal sacs

The present study was designed to investigate the effects of aqueous fruit extract of Momordica charantia (MC), a traditional medicinal plant, on the transport of fluid in vitro. Everted intestinal sacs from rats were mounted in an organ bath containing Krebs solution. We compared the effect of MC extract on water transport with increasing inorganic phosphate concentration with or without d‐glucose in the buffer. In the control experiments, fluid uptake was enhanced significantly (P < 0.05) at high inorganic phosphate concentration (8–10 mm) in the presence of 5.5 mmd‐glucose. Addition of 3.0 mg/mL MC extract to the serosal side inhibits the uptake of fluid significantly (P < 0.05). At high inorganic phosphate concentration (8–10 mm), fluid uptake was not inhibited (P > 0.05) when incubated with 3.0 mg/mL MC fruit extract. It is hypothesized that an increase in inorganic phosphate enhances oxidative phosphorylation thereby increasing the fluid uptake across everted intestinal sacs of rat. These findings seem to indicate that the MC‐induced reduction on intestinal fluid absorption capacity could be mainly the result of an interference with the carrier‐mediated coupled entrance of glucose and Na+ across the brush‐border membrane.

Stimulatory effects of Antidesma madagascariense on D-glucose, L-tyrosine, fluid and electrolyte transport across rat everted intestine, comparable to insulin action in vitro.

Abstract Medicinal plants are believed to be an important source of potential therapeutic agents. This study investigates the effects of Antidesma madagascariense (AM) extract on the transport of D-glucose, L-tyrosine, fluid and electrolytes (Na+ and K+) across rat everted intestinal sacs. These sacs were mounted in an organ bath containing Krebs-Henseleit bicarbonate (KHB) buffer. Experimental findings showed that incubation with graded aqueous AM extracts above 0.375 mg/mL significantly (P<0.05) stimulated the mucosal disappearance and serosal appearance of glucose and fluid. The concentration of glucose accumulated in the intestinal tissues also increased significantly (P<0.05) compared to that found in the controls. Transport of the amino acid L-tyrosine was not significantly enhanced (P>0.05) when incubated with increasing concentrations of AM extract. Effects on electrolyte (K+ and Na+) transport were assessed. Na+ uptake and transport was significantly enhanced (P<0.05) when incubated with 0.75 mg/mL AM extract; however, K+ transport was not significantly enhanced (P>0.05). For comparison, insulin (1 and 2 units/mL) was incubated in the mucosal solution. Aqueous AM extract produced similar stimulatory effects on the transport of glucose, fluid and Na+ as were found with insulin. It is hypothesised that bioactive phytochemicals such as flavonoids, alkaloids, leucoanthocyanins, phenols and saponins from AM leaf extract might interfere with the Na+/glucose carrier, thereby enhancing the transport of glucose, Na+ and fluid across rat everted intestinal sacs. Thus, AM may represent a possible alternative dietary supplement for the treatment of type 2 diabetes.

Effects of Aphloia theiformis on key enzymes related to diabetes mellitus

Abstract Context: Aphloia theiformis (Vahl.) Benn. (Flacourtiaceae) (AT) is traditionally used for the management of diabetes mellitus (DM), but there is no scientific data regarding activity against enzymes linked to this condition. Objective: To evaluate the kinetics of AT on key enzymes inhibition related to DM, and establish the antioxidant profile of AT. Materials and methods: Dried powdered AT leaves were used to prepare crude methanol extract (70% v/v) (CME). Kinetics of CME (5000 to 156.25 μg/mL) on α-amylase, α-glucosidase, and lipase inhibition were studied. CME was partitioned using solvents of increasing polarity and kinetics of enzyme inhibition of each fraction (1000–31.25 μg/mL) was evaluated. Potent fractions were combined to assess any synergistic effect. Total phenol, flavonoid, tannin, anthocyanin contents, and antioxidant capacity of AT was evaluated using standard spectrophotometric methods. Results: CME, ethyl acetate, and n-butanol fractions showed potent inhibitory activities against the enzymes with IC50 ranging from 22.94–939.97 μg/mL. Significant (p < 0.05) reduction in IC50 (15.72 and 157.03 μg/mL against α-amylase and lipase, respectively) was observed when ethyl acetate and n-butanol fractions were combined; showing synergism. The extracts showed noncompetitive inhibition against α-amylase and α-glucosidase. Ethyl acetate, n-butanol fractions, and CME showed highest antioxidant capacities (0.44–1.41 μg GAE/mg sample), and phenol content (211.74-675.53 μg GAE/mg sample). Conclusion: This study supports the use of AT in the management of DM and provides the rationale for bioactivity guided isolation and characterization of compounds from the ethyl acetate and n-butanol fractions.

In vitro and in silico perspectives on biological and phytochemical profile of three halophyte species—A source of innovative phytopharmaceuticals from nature

BACKGROUND Halophytes are considered as valuable sources of traditional drugs in different countries. PURPOSE The present study aimed to evaluate biological and chemical fingerprints of three halophytes (Arthrocnemum macrostachyum (Moric.) C, Koch, Halimione portulacoides (L.) Aellen and Salicornia europaea L.). MATERIALS AND METHODS The antioxidant and enzymatic inhibitory potential (acetylcholinesterase, butyrylcholinesterase, α-amylase, α-glucosidase, and tyrosinase) were assessed. The total phenolic, flavonoid contents, and the chemical profiles were appraised using the ultra-high performance liquid chromatography-electrospray ionization-tandem mass spectrometry. Molecular docking was conducted to provide additional insights of molecular interactions of the enzymes/phytochemicals. RESULTS Ethyl acetate extract was the most efficient extract, with A. macrostachyum being the most potent towards DPPH and ABTS radicals and phosphomolybdenum assay. Ethyl acetate extract of A. macrostachyum was also the best reducing agent (CUPRAC and FRAP assays). Methanol and ethyl acetate extract of A. macrostachyum, H. portulacoides, and S. europaea showed significant enzyme inhibition potential. Ethyl acetate extract of A. macrostachyum showed the highest total phenolic (29.54 ± 0.78 mgGAEs/g extract) while the ethyl acetate extract of S. europaea was more abundant in flavonoids (18.26 ± 0.11 mgREs/g extract). Phytochemical profiling allowed the identification of several components in the methanolic extracts (16 in A. macrostachyum, 14 in H. portulacoides, and 11 in S. europaea), with quinic acid, p-coumaric acid, and rhamnetin being most abundant. Docking studies revealed that the above compounds showed scores for the enzymes tested. CONCLUSION The three halophytes studies could be considered as potential sources of biologically-active compounds for novel phytopharmaceuticals development.