Rhinacanthus nasutus Improves the Levels of Liver Carbohydrate, Protein, Glycogen, and Liver Markers in Streptozotocin-Induced Diabetic Rats

Medicinal herbs and their metabolites with biological potential to protect and combat liver toxicity and its disorders: A review

The liver is an essential organ that helps the body with immunity, metabolism, and detoxification, among other functions. Worldwide, liver illnesses are a leading cause of mortality and disability. There are few effective treatment choices, but they frequently have unfavorable side effects. Investigating the potential of medicinal plants and their bioactive phytoconstituents in the prevention and treatment of liver disorders has gained more attention in recent years. An assessment of the hepatoprotective potential of medicinal plants and their bioactive secondary metabolites is the goal of this thorough review paper. To determine their hepatoprotective activity, these plants were tested against liver toxicity artificially induced in rats, mice and rabbits by chemical agents such as carbon tetrachloride (CCl4), paracetamol (PCM), thioacetamide (TAA), N-nitrosodiethylamine, d-galactosamine/lipopolysaccharide, antitubercular medicines (rifampin, isoniazid) and alcohol. To find pertinent research publications published between 1989 and 2022, a comprehensive search of electronic bibliographic databases (including Web of Science, SpringerLink, ScienceDirect, Google Scholar, PubMed, Scopus, and others) was carried out. The investigation comprised 203 plant species from 81 families in total. A thorough discussion was mentioned regarding the hepatoprotective qualities of plants belonging to several families, such as Fabaceae, Asteraceae, Lamiaceae, and Euphorbiaceae. The plant groups Asteraceae and Fabaceae were the most frequently shown to have hepatoprotective properties. The phytochemical constituents namely flavonoids, phenolic compounds, and alkaloids exhibited the highest frequency of hepatoprotective action. Also, some possible mechanism of action of some active constituents from medicinal plants was discussed in brief which were found in some studies. In summary, the information on medicinal plants and their potentially hepatoprotective bioactive phytoconstituents has been consolidated in this review which emphasizes the importance of further research to explore the efficacy and safety of these natural remedies for various liver ailments.

Preparation, in vitro and in vivo evaluation of pinocembrin-loaded TPGS modified liposomes with enhanced bioavailability and antihyperglycemic activity

PURPOSE

To prepare polyethylene glycol succinate-vitamin E modified pinocembrin (PCB)-loaded liposomes (PCBT-liposomes) and evaluate PCBT-liposomal pharmacokinetics and antihyperglycemic activity.

SIGNIFICANCE

The novel PCBT-liposomes demonstrated a promising application prospect as a nano drug carrier for future research.

METHODS

Thin film dispersion was used to prepare PCBT-liposomes. We measured a series of characterization, followed by in vitro cumulative release, in vivo pharmacokinetic study, and antihyperglycemic activity evaluation.

RESULTS

PCBT-liposomes displayed spherical and bilayered nanoparticles with mean particle size (roughly 92 nm), negative zeta potential (about -26.650 mV), high drug encapsulation efficiency (87.32 ± 1.34%) and good storage (at 4 or 25 °C) stability during 48 h after hydration. The cumulative release rate of PCBT-liposomes was markedly higher than free PCB in four different pH media. In vivo investigation showed that PCBT-liposomes could obviously improve oral bioavailability of PCB by 1.96 times, whereas the C_max, MRT_0-t, and T_1/2 of PCBT-liposomes were roughly 1.700 ± 0.139 µg·mL^-1, 12.695 ± 1.647 h, and 14.244 h, respectively. In terms of biochemical analysis, aspartate amino-transferase (AST), alanine amino-transferase (ALT), interleukin-1 (IL-1), and tumor necrosis factor-α (TNF-α) concentrations in serum of diabetic mice were respectively decreased 28.28%, 17.23%, 17.77%, and 8.08% after PCBT-liposomal treatment.

CONCLUSION

These results show PCBT-liposomal preparation as an excellent nano-carrier which has the potential to improve water solubility, bioavailability, and antihyperglycemic activity of PCB, amid broadening the application of PCB in the clinical settings.

Ethnobotanical Survey on Bitter Tea in Taiwan

Ethnopharmacological evidence: In Taiwan, herbal tea is considered a traditional medicine and has been consumed for hundreds of years. In contrast to regular tea, herbal teas are prepared using plants other than the regular tea plant, Camellia sinensis (L.) Kuntze. Bitter tea (kǔ-chá), a series of herbal teas prepared in response to common diseases in Taiwan, is often made from local Taiwanese plants. However, the raw materials and formulations have been kept secret and verbally passed down by store owners across generations without a fixed recipe, and the constituent plant materials have not been disclosed.

Aim of the study: The aim was to determine the herbal composition of bitter tea sold in Taiwan, which can facilitate further studies on pharmacological applications and conserve cultural resources.

Materials and methods: Interviews were conducted through a semi-structured questionnaire. The surveyed respondents were traditional sellers of traditional herbal tea. The relevant literature was collated for a systematic analysis of the composition, characteristics, and traditional and modern applications of the plant materials used in bitter tea. We also conducted an association analysis of the composition of Taiwanese bitter tea with green herb tea (qing-cao-cha tea), another commonly consumed herbal tea in Taiwan, as well as herbal teas in neighboring areas outside Taiwan.

Results: After visiting a total of 59 stores, we identified 32 bitter tea formulations and 73 plant materials. Asteraceae was the most commonly used family, and most stores used whole plants. According to a network analysis of nine plant materials used in high frequency as drug pairs, Tithonia diversifolia and Ajuga nipponensis were found to be the core plant materials used in Taiwanese bitter tea.

Conclusion: Plant materials used in Taiwanese bitter tea were distinct, with multiple therapeutic functions. Further research is required to clarify their efficacy and mechanisms.

An Ethnobotanical Study on Qīng-Căo-Chá Tea in Taiwan

Herbal tea, a beverage prepared from a variety of plant materials excluding the leaves of the tea plant Camellia sinensis (L.) Kuntze of the family Theaceae, for a long time, has been consumed by most Chinese people for preventive and/or therapeutic health care. Usually, it is brewed or prepared as a decoction of local plants in water. The qīng-căo-chá tea, a commercial herbal tea, is the most common among many differently formulated herbal teas in Taiwan. For hundreds of years, qīng-căo-chá tea has played an important role in the prevention and treatment of diseases associated with the environmental conditions in Taiwan. However, research studies in this field have been insufficient. The raw material formulas of qīng-căo-chá tea have always been passed down from “masters” to “apprentices.” Hence, there is no systematic collation or record, and, therefore, there is a need to assess and confirm the composition, safety, and effectiveness of the raw materials. This study aimed to document the uses of Taiwan's qīng-căo-chá tea through a semi-structured interview survey and investigate the background of traditional practitioners, tea compositions, and plant origins and uses. This will improve our understanding of the knowledge inherited by the practitioners and the theoretical basis of the medicinal uses of these teas. In our field investigation, we visited 86 shops and assessed 71 raw ingredients of qīng-căo-chá tea. A semi-structured questionnaire was used to conduct the interviews. During the interviews, in addition to written records, audio and video recordings were made, and photographs were taken with the permission of the interviewees. The qīng-căo-chá raw materials have long been used as herbal teas, although more research should clarify their efficacy and safety. Traditional sellers of qīng-căo-chá tea were mainly males, and most shops have been in operation for more than 71 years. Some of the raw materials were derived from multiple sources, including different plants, and were often mixed without any safety concerns. To our knowledge, this is the first systematic ethnobotanical study on qīng-căo-chá tea that assesses and confirms its herbal ingredients. Our study represents a reference for herbal teas in Taiwan that can be used by the public and regulatory agencies.

Antidiabetic Potential of Syzygium sp.: An Overview

Diabetes, characterized by hyperglycemia, is one of the most significant metabolic diseases, reaching alarming pandemic proportions. It can be due to the defects in insulin action, or secretion, or both. The global prevalence of diabetes is estimated at 425 million people in 2017, and expected to rise to 629 million by 2045 due to an increasing trend of unhealthy lifestyles, physical inactivity, and obesity. Several treatment options are available to diabetics, however, some of the antidiabetic drugs result in adverse side effects such as hypoglycemia. Hence, there has been a proliferation of studies on natural products with antidiabetic effects, including plants from the Myrtaceae family, such as Psidium guajava, Eucalyptus globulus,Campomanesia xanthocarpa, and more significantly, Syzygium sp. Previous studies have shown that a number of Syzygium species had potent antidiabetic effects and were safe for consumption. This review aims to discuss the antidiabetic potential of Syzygium sp., based on in vitro and in vivo evidence.

Gongronema latifolium leaf extract modulates hyperglycaemia, inhibits redox imbalance and inflammation in alloxan-induced diabetic nephropathy

Background

Gongronema latifolium leaf is used traditionally to treat diabetes and other diseases. The present study aimed to provide the modulatory effect of G. latifolium on hyperglycemia, inhibitory effect of redox imbalance and inflammation in alloxan-induced nephropathy in Wistar rats.

Methods

Alloxan monohydrate was used to induce diabetes by an intraperitoneal injection of (150 mg/kg). Three diabetic groups were administered aqueous leaf extract of G. latifolium at 6.36, 12.72 and 25.44 mg/kg bodyweight (BW) respectively; a group was administered with metformin (5 mg/kg BW), while the other two were served as positive and negative control. Thereafter, fasting blood glucose, antioxidant enzymes, malondialdehyde (MDA) level, interleukin 2 and 6 were determined.

Results

G. latifolium leaf significantly (p < 0.05) reduced the alloxan-induced increases in blood glucose, MDA, interleukin 2 and interleukin 6 level and increased the alloxan-induced decreases in superoxide dismutase, catalase, glutathione peroxidase, glutathione reduced and glutathione transferase activity. All these changes compared with those of metformin-treated diabetic rats.

Conclusion

The data from this study suggest that G. latifolium modulates glucose homeostasis as well as inhibiting redox imbalance and inflammation in diabetic rats, which may be attributed to the effects of its phytochemical constituents such as saponins, flavonoids and alkaloids. It also indicated that inhibition of inflammatory cytokines and redox imbalance are likely mechanisms by which G. latifolium leaf exert its antidiabetic action.

Supplementation of Stingless Bee Honey from Heterotrigona itama Improves Antiobesity Parameters in High-Fat Diet Induced Obese Rat Model

Heterotrigona itama is a common stingless bee species found in Southeast Asia. Studies on the health benefits of its honey are limited in comparison with other stingless bee species. This study examines the antiobesity benefits found in stingless bee honey (SBH) from H. itama. The parameters used to measure the benefits were weight change, morphological structures, and biochemical characteristics. The research was conducted by using rats that were given a high-fat diet (HFD). In total 48 male Sprague Dawley (SD) rats were given a formulated HFD to increase the levels of obesity, the HFD was administered with a value of 0.68 g/cm2. The duration of the treatment was six weeks, and the results show that the induction obesity using the HFD was successful. Following this, the rats were then treated with SBH (at dosages of 1000 mg/kg, 750 mg/kg or 500 mg/kg), with orlistat or with a placebo. Compared with typical obesity treatment methods, the one that used the three dosages of SBH showed a higher reduction in body mass index (BMI), percentage of body weight gain, adiposity index, and relative organ weight (ROW). The levels of liver enzymes (ALT, AST, and ALP) were also significantly lower in SBH-treated groups. The levels of triglycerides and LDL-cholesterol were significantly lower, while the level of HDL-cholesterol was significantly higher in comparison with the control obese group. In terms of morphological structures, the number of adipocyte cells was reduced, and the hepatocytes found in the liver were less prone to rupturing when treated with SBH. In conclusion, the administration of SBH led to an improvement in indicators associated with obesity reduction. SBH also possesses a hepatoprotective potential which can reduce the health risks related to obesity.

Ameliorative Activity of Ethanolic Extract of Artocarpus heterophyllus Stem Bark on Alloxan-induced Diabetic Rats

Purpose: Diabetes mellitus is one of the major endocrine disorders, characterized by impaired insulin action and deficiency. Traditionally, Artocarpus heterophyllus stem bark has been reputably used in the management of diabetes mellitus and its complications. The present study evaluates the ameliorative activity of ethanol extract of Artocarpus heterophyllus stem bark in alloxan-induced diabetic rats.

Methods: Diabetes mellitus was induced by single intraperitoneal injection of 150 mg/kg body weight of alloxan and the animals were orally administered with 50, 100 and 150 mg/kg body weight ethanol extract of Artocarpus heterophyllus stem bark once daily for 21 days.

Results: At the end of the intervention, diabetic control rats showed significant (p<0.05) weight reduction, abnormal haematological parameters, high serum lipids (except high density lipoprotein) concentrations, increased creatinine, bilirubin and urea levels with decreased in albumin level when compared with non-diabetic control rats. All these alterations were reverted to normal after administered with different doses of ethanol extract of Artocarpus heterophyllus stem bark most especially at 150 mg/kg body weight which exhibited no significant (p>0.05) different with non-diabetic rats.

Conclusion: The results suggest that ethanol extract of Artocarpus heterophyllus stem bark may be useful in ameliorating complications associated with diabetes mellitus patients.

Rhinacanthins-rich Extract Enhances Glucose Uptake and Inhibits Adipogenesis in 3T3-L1 Adipocytes and L6 Myotubes

Background:

Obesity is one of the imperative dynamics in the incidence and intensification of type 2 diabetes mellitus (T2DM). Rhinacanthus nasutus leaf extracts are previously reported for their antidiabetic and antiobesity potential.

Objective:

The present study was performed to evaluate glucose uptake stimulatory and antiadipogenic activities of a standardized rhinacanthins-rich extract (RRE) and its marker compounds namely rhinacanthin-C (RC), rhinacanthin-D (RD), and rhinacanthin-N (RN) in 3T3-L1 and L6 cells.

Materials and Methods:

RRE was prepared by a green extraction process, and the marker compounds (RC, RD, and RN) were isolated from the RRE using a silica gel column chromatography. Glucose uptake stimulation in both 3T3-L1 and L6 cells was performed by quantification of residual glucose in the media using glucose oxidase kit. Antiadipogenic activity in 3T3-L1 adipocytes was performed by intracellular lipids quantification using oil red O dye.

Results:

At the highest effective dose, RRE (20 μg/mL) exhibited satisfactory glucose uptake stimulatory effect in 3T3-L1 adipocytes that equivalent to RN (20 μg/mL) and the positive control insulin (0.58 μg/mL) but higher than RC (20 μg/mL) and RD (20 μg/mL). In addition, treatments of L6 myotubes showed that RRE (2.5 μg/mL) exhibited potent and equivalent glucose uptake stimulation (>80%) to RC (2.5 μg/mL) and the standard drugs, insulin (2.90 μg/mL) and metformin (219.5 μg/mL), but higher than RD (2.5 μg/mL) and RN (2.5 μg/mL). Furthermore, RRE (20 μg/mL) exhibited potent antiadipogenic effect in 3T3-L1 adipocytes, which equivalent to RC (20 μg/mL) but higher than RD (20 μg/mL) and RN (20 μg/mL).

Conclusions:

The undertaken study suggests that RRE could be used as an effective remedy in the treatment of obesity-associated T2DM.

SUMMARY

Rhinacanthins-rich extract and its marker compounds showed potent glucose uptake stimulatory activity in 3T3-L1 adipocytes and L6 myotubes

Rhinacanthins-rich extract and rhinacanthin-C showed comparable antiadipogenic effect in 3T3-L1 adipocytes

RRE could be used as an effective remedy in the treatment of obesity-associated T2DM.

Abbreviations used: T2DM: Type-2 diabetes mellitus; RRE: Rhinacanthins-rich extract; RC: Rhinacanthin-C; RD: Rhinacanthin-D; RN: Rhinacanthin-N; α-MEM: α-Minimum essential medium; DMEM: Dulbecco's modified Eagle's medium; HS: Horse serum; FBS: Fetal bovine serum; BSA: Bovine serum albumin; IBMX: 3-isobutyl-1-methylxanthine; MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; GO: Glucose oxidase; NMR: Nuclear magnetic resonance; HPLC: High-performance liquid chromatography.

Proteomic Analysis of Differentially-Expressed Proteins in the Liver of Streptozotocin-Induced Diabetic Rats Treated with Parkia biglobosa Protein Isolate

Protein isolate from Parkia biglobosa seeds is believed to possess excellent anti-diabetic properties. The purpose of this study was to identify differentially expressed proteins in liver of streptozotocin-induced diabetic rats treated with Parkia biglobosa seeds protein isolate (PBPi). In this study, total proteins extracted from rat liver were separated on one-dimensional SDS polyacrylamide gel (1D SDS-PAGE) and stained with Coomassie brilliant blue (CBB) to visualize protein bands. We observed that protein bands in the region of 10-15 kDa were altered by the different treatments; these bands were selected and excised for in-gel digestion and peptide extraction followed by nLC-MS, MALDI-TOF MS, and LIFT MS/MS. A database search with the Mascot algorithm positively identified four differentially expressed proteins. These proteins are known to be responsible for diverse biological functions within various organs and tissues. The present result gives insight and understanding into possible molecular mechanisms by which streptozotocin causes various alterations in proteins found in the liver of diabetic rats and the possible modulatory role of PBPi in the management of streptozotocin-induced diabetes.

Superoxide Scavenging and Antiglycation Activity of Rhinacanthins-rich Extract Obtained from the Leaves of Rhinacanthus nasutus

Background:

Oxidative stress and nonenzymatic protein glycation lead to serious diabetic complications that increase the risk of mortality. Rhinacanthus nasutus leaf crude extracts are previously reported for their antidiabetic, antiglycation, and antioxidant potential.

Objective:

The present study was performed to prepare a standardized rhinacanthins-rich extract (RRE) and evaluate its superoxide scavenging and antiglycation effects as compared to its marker compounds, namely, rhinacanthin-C (RC), rhinacanthin-D (RD), and rhinacanthin-N (RN).

Materials and Methods:

RRE was obtained by microwave-assisted green extraction along with a simple step of fractionation using Amberlite^® column. RC, RD, and RN were isolated from the RRE using silica gel column chromatography. Superoxide scavenging activity was performed by cyclic voltammetry, and fructose-mediated human serum albumin glycation model was used for antiglycation activity. In silico studies were conducted to identify the structure-activity relationships of rhinacanthins.

Results:

On the basis of kinetic measurements, RRE exhibited the most potent antioxidant activity via E_rC_i mechanism, with a 50% inhibitory concentration (IC₅₀) value of 8.0 μg/mL, antioxidant capacity of 39439 M⁻¹, and binding constant of 45709 M⁻¹. Antiglycation assay showed that RRE exhibited almost equivalent glycation inhibitory effect to that of RC, with IC₅₀ values of 39.7 and 37.3 μg/mL, respectively, but higher than that of RD (IC₅₀ of 50.4 μg/mL), RN (IC₅₀ of 89.5 μg/mL), as well as the positive control, rutin (IC₅₀ of 41.5 μg/mL).

Conclusions:

The potent superoxide scavenging and albumin glycation inhibitory effect of RRE rationalized its therapeutic application in various chronic diseases, especially in the complications of diabetes.

SUMMARY

Rhinacanthins-rich extract (RRE) exhibited potent superoxide scavenging activity

RRE and rhinacanthin-C showed remarkable and comparable antiglycation effect

Rhinacanthins exhibited antiglycation activity by masking specific residues of albumin.

Abbreviations used: RRE: Rhinacanthins-rich extract; RC: Rhinacanthin-C; RD: Rhinacanthin-D; RN: Rhinacanthin-N; IC₅₀: 50% inhibitory concentration; Kao: Antioxidant activity coefficient; Kb: Binding constant; E_rC_i: Reversible electron transfer followed by an irreversible chemical reaction; DM: Diabetes mellitus; AGEPs: Advanced glycation end products; NMR: Nuclear magnetic resonance; HPLC: High-performance liquid chromatography; CV: Cyclic voltammetry; DMSO: Dimethyl sulfoxide; Ipa: Anodic peak current; Ipc: Cathodic peak current; HSA: Human serum albumin; MOE: Molecular operating environment; PASSonline: Online prediction of activity spectra for substances.

Antihyperglycemic and Antihyperlipidemic Activity of Hydroponic Stevia rebaudiana Aqueous Extract in Hyperglycemia Induced by Immobilization Stress in Rabbits

Diabetes mellitus (DM) is a serious worldwide problem related to human hyperglycemia. Thus, herbal preparations with antihyperglycemic properties especially leaf extracts of hydroponic Stevia rebaudiana (SR) would be useful in hyperglycemia treatment. The antihyperglycemic potential of this medicinal plant grown using hydroponics methods has been evaluated. Significant reduction of some biochemical characteristics for sugars and fatty acids in blood, liver, and muscle especially fasting glucose levels, serum triglycerides, LDL-cholesterol, total cholesterol levels, and increased HDL-cholesterol ones was shown with SR aqueous extract treatment. Therefore, the aqueous extract of SR is suggested to have antihyperglycemic and antihyperlipidemic activity and to restore liver and muscle glycogen levels (hepatoprotective effects) in hyperglycemia induced by immobilization stress in rabbits and might be recommended for treatment of DM (hyperglycemia).

Hypoglycaemic activity of Mathurameha, a Thai traditional herbal formula aqueous extract, and its effect on biochemical profiles of streptozotocin-nicotinamide-induced diabetic rats

BACKGROUND

The Thai traditional herbal formula-Mathurameha, consisting of 26 medicinal plants, has been used as an alternative and complementary medicine for diabetes treatment in Wangnamyen Hospital, Thailand. To provide scientific evidences on the efficacy and safety of this herbal formula, in vivo hypoglycaemic activity, effect on serum biochemical profiles and acute toxicity were investigated.

METHODS

Experimental type 2 diabetes was induced in male Sprague-Dawley rats by intraperitoneal injection of nicotinamide 15 min prior to intravenous injection of streptozotocin. The most effective extract from the oral glucose tolerant test (OGTT) was administered daily via the oral route to diabetic rats for 2 weeks. Two-hour postprandial plasma glucose (2h-PPG) levels were measured on days 0, 7, and 14. Biochemical data were measured at the end of daily oral administration experiment.

RESULTS

Aqueous extract of the herbal formula was the most potent extract for improving glucose tolerance of streptozotocin-nicotinamide-induced diabetic rats after single oral administration. After 2 weeks of daily oral administration, the aqueous extract showed a dose-dependent glucose lowering effect. At doses of 12.5, 25, and 50 mg/kg, the 2h-PPG level of diabetic rats decreased by 3.32%, 15.78%, and 17.94%, respectively. Most of the biochemical profiles of diabetic rats were improved, including the total cholesterol (TC), alkaline phosphatase (ALP), total protein, albumin, globulin, creatinine, and uric acid levels. The significantly increased triglyceride (TG) level observed in treated diabetic rats indicated a lack of a beneficial effect of the extract on lipid homeostasis. Nevertheless, there were no signs or symptoms of acute toxicity observed after oral administration of aqueous extract (5 g/kg) to both male and female rats.

CONCLUSIONS

The results revealed that the herbal formula aqueous extract has hypoglycaemic activity, beneficial effects on biochemical profiles and a lack of acute toxicity. This study confirms the efficacy and safety of the Mathurameha herbal formula used for treating type 2 diabetes mellitus.

Four-Week Consumption of Malaysian Honey Reduces Excess Weight Gain and Improves Obesity-Related Parameters in High Fat Diet Induced Obese Rats

Many studies revealed the potential of honey consumption in controlling obesity. However, no study has been conducted using Malaysian honey. In this study, we investigated the efficacy of two local Malaysian honey types: Gelam and Acacia honey in reducing excess weight gain and other parameters related to obesity. The quality of both honey types was determined through physicochemical analysis and contents of phenolic and flavonoid. Male Sprague-Dawley rats were induced to become obese using high fat diet (HFD) prior to introduction with/without honey or orlistat for four weeks. Significant reductions in excess weight gain and adiposity index were observed in rats fed with Gelam honey compared to HFD rats. Moreover, levels of plasma glucose, triglycerides, and cholesterol, plasma leptin and resistin, liver enzymes, renal function test, and relative organ weight in Gelam and Acacia honey treated groups were reduced significantly when compared to rats fed with HFD only. Similar results were also displayed in rats treated with orlistat, but with hepatotoxicity effects. In conclusion, consumption of honey can be used to control obesity by regulating lipid metabolism and appears to be more effective than orlistat.

The inhibitory activity of herbal medicines on the keys enzymes and steps related to carbohydrate and lipid digestion

BACKGROUND

Obesity and overweight are consistently associated with metabolic disorders including hyperglycemia and hyperlipidemia. Herbal medicines have been currently suggested as an alternative source of potentially useful antihyperglycemic, antihyperlipidemic, antioxidant activities. The objective of this study was to assess the in vitro inhibitory effects of eleven herbal medicines on carbohydrate and lipid digestive enzymes and the key steps of lipid digestion including the inhibition of micelle formation and the ability to bind bile acid. In addition, antioxidant activity of herbal medicines was also investigated.

METHODS

α-Glucosidase, pancreatic α-amylase, pancreatic lipase, and pancreatic cholesterol esterase inhibitory activities of aqueous extract of herbal medicines were measured using the enzymatic colorimetric assay. The formation of cholesterol micelles was determined using the cholesterol assay kit. The bile acid binding was measured using the colorimetric assay. Antioxidant activities were assessed by using four methods including Trolox equivalent antioxidant capacity (TEAC), oxygen radical absorbance capacity ORAC), superoxide radical scavenging activity (SRSA), and hydroxyl radical scavenging activity (HRSA).

RESULTS

The extracts (1 mg/mL) markedly inhibited intestinal maltase (5.16 - 44.33 %), sucrase (1.25-45.86 %), pancreatic α-amylase (1.75-12.53 %), pancreatic lipase (21.42-85.93 %), and pancreatic cholesterol esterase (2.92-53.35 %). The results showed that all extracts exhibited the inhibitory activity against pancreatic lipase with the IC₅₀ values ranging from 0.015 to 4.259 mg/mL. In addition, the incorporation of cholesterol into micelles was inhibited by the extracts (6.64-33.74 %). The extracts also bound glycodeoxycholic acid (9.9-15.08 %), taurodeoxycholic acid (12.55-18.18 %), and taurocholic acid (11.91 - 18.4 %). Furthermore, the extracts possessed various antioxidant activities including the TEAC values (0.50 - 4.70 μmol trolox/mg dried extract), the ORAC values (9.14-44.41 μmol trolox/mg dried extract), the SRSA (0.31 - 18.82 mg trolox/mg dried extract), and the HRSA (0.05-2.29 mg trolox/mg dried extract). The findings indicated that Syzygium aromaticum, Phyllanthus amarus, Thunbergia laurifolia were the effective promising antihyperglycemic and antihyperlipidemic agents. Statistical analysis demonstrated strong positive significant correlations between the contents of phenolic compounds and % inhibition of pancreatic lipase (r = 0.885, p < 0.001), % inhibition of pancreatic cholesterol esterase (r = 0.761, p < 0.001), and the TEAC value (r = 0.840, p < 0.001). Furthermore, there was a strongly positive correlation between the TEAC value and % inhibition of pancreatic cholesterol esterase (r = 0.851, p < 0.001) and % inhibition of pancreatic lipase (r = 0.755, p < 0.001).

CONCLUSIONS

Three herbal medicines including Syzygium aromaticum, Thunbergia laurifolia, and Phyllanthus amarus markedly inhibited the intestinal α-glucosidase, pancreatic α-amylase, pancreatic lipase, and pancreatic cholesterol esterase. They also reduced formation of cholesterol micelle and bound bile acid. The findings indicate that these herbal medicines might be a promising agent for antihyperglycemic, antihyperlipidemic, and antioxidant activities.

Antioxidant, antidiabetic and hypolipidemic effects of Tulbaghia violacea Harv. (wild garlic) rhizome methanolic extract in a diabetic rat model

Background

The prevalence of diabetes mellitus (DM) continues to rise alarmingly despite years of intensive research. The need to explore alternative remedies such as traditional phytotherapy has therefore become increasingly important in the management and treatment of DM.

Methods

Diabetes was induced by a single intraperitoneal (i.p) injection of streptozotocin (40 mg/kg.b.w) in male Wistar rats. The rats were divided into 5 groups as follows: non-diabetic control fed distilled water, diabetic control fed distilled water, diabetic group treated with Tulbaghia violacea (TVL) (60 mg/kg.b.w), diabetic group treated with TVL (120 mg/kg.b.w), and diabetic group treated with glibenclamide (10 mg/kg.b.w). Food and water intake, as well as urine output were measured daily, whilst body weight and fasting blood glucose were monitored weekly. On day 42, an oral glucose tolerance test was performed on all groups. After 7 weeks, the animals were sacrificed by halothane overdose, blood was removed by cardiac puncture and tissues were harvested. Assays were performed for the determination of plasma insulin, liver glycogen content, lipid peroxidation, antioxidant enzyme levels, plasma nitric oxide levels and serum lipid and liver enzyme levels.

Results and Discussion

TVL treatment improved body weights, significantly reduced fasting blood glucose levels, improved glucose tolerance and significantly increased plasma insulin and liver glycogen content. TVL treatment also reduced liver thiobarbituric acid reactive substances (TBARS) levels, increased liver superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx) and increased plasma nitric oxide (NO) levels. Furthermore, TVL administration reduced serum triglycerides, VLDL, total-cholesterol levels and increased HDL-cholesterol levels. TVL also reduced serum levels of liver enzymes, alanine aminotransferase (ALT) and aspartate aminotransferase (AST).

Conclusion

Data obtained in this study demonstrated the hypoglycemic, antioxidant, hepatoprotective and hypolipidemic effects of TVL in STZ-induced diabetic rats.