Traditional Chinese medicine (TCM) is an important part of primary health care in Asian countries that has utilized complex herbal formulations (consisting 2 or more medicinal herbs) for treating diseases over thousands of years. There seems to be a general assumption that the synergistic therapeutic effects of Chinese herbal medicine (CHM) derive from the complex interactions between the multiple bioactive components within the herbs and/or herbal formulations. However, evidence to support these synergistic effects remains weak and controversial due to several reasons, including the very complex nature of CHM, misconceptions about synergy and methodological challenges to study design. In this review, we clarify the definition of synergy, identify common errors in synergy research and describe current methodological approaches to test for synergistic interaction. We discuss the strengths and weaknesses of these models in the context of CHM and summarize the current status of synergy research in CHM. Despite the availability of some scientific data to support the synergistic effects of multi-herbal and/or herb-drug combinations, the level of evidence remains low, and the clinical relevancy of most of these findings is undetermined. There remain significant challenges in the development of suitable methods for synergistic studies of complex herbal combinations.

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PurposeThe optimal health benefits of curcumin are limited by its low solubility in water and corresponding poor intestinal absorption. Cyclodextrins (CD) can form inclusion complexes on a molecular basis with lipophilic compounds, thereby improving aqueous solubility, dispersibility, and absorption. In this study, we investigated the bioavailability of a new γ-cyclodextrin curcumin formulation (CW8). This formulation was compared to a standardized unformulated curcumin extract (StdC) and two commercially available formulations with purported increased bioavailability: a curcumin phytosome formulation (CSL) and a formulation of curcumin with essential oils of turmeric extracted from the rhizome (CEO).MethodsTwelve healthy human volunteers participated in a double-blinded, cross-over study. The plasma concentrations of the individual curcuminoids that are present in turmeric (namely curcumin, demethoxycurcumin, and bisdemethoxycurcumin) were determined at baseline and at various intervals after oral administration over a 12-h period.ResultsCW8 showed the highest plasma concentrations of curcumin, demethoxycurcumin, and total curcuminoids, whereas CSL administration resulted in the highest levels of bisdemethoxycurcumin. CW8 (39-fold) showed significantly increased relative bioavailability of total curcuminoids (AUC0−12) in comparison with the unformulated StdC.ConclusionThe data presented suggest that γ-cyclodextrin curcumin formulation (CW8) significantly improves the absorption of curcuminoids in healthy humans.

In traditional Chinese medicine, Gynostemma pentaphyllum (Thunb.) Makino is a herbal drug of extreme versatility and has been extensively researched in China. The dammarane saponins isolated from Gynostemma pentaphyllum, namely gypenosides or gynosaponins, are believed to be the active components responsible for its various biological activities and reported clinical effects. This review attempts to encompass the available literature on Gynostemma pentaphyllum, from its cultivation to the isolation of its chemical entities and a summary of its diverse pharmacological properties attributed to its gypenoside content. Other aspects such as toxicology and pharmacokinetics are also discussed. In vitro and in vivo evidence suggests that Gynostemma pentaphyllum may complement the popular herbal medicine, Panax ginseng, as it also contains a high ginsenoside content and exhibits similar biological activities. Abbreviations

Nuxia oppositifolia is traditionally used in diabetes treatment in many Arabian countries; however, scientific evidence is lacking. Hence, the present study explored the antidiabetic and antioxidant activities of the plant extracts and their purified compounds. The methanolic crude extract of N. oppositifolia was partitioned using a two-solvent system. The n-hexane fraction was purified by silica gel column chromatography to yield several compounds including katononic acid and 3-oxolupenal. Antidiabetic activities were assessed by α-amylase and α-glucosidase enzyme inhibition. Antioxidant capacities were examined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) scavenging assays. Further, the interaction between enzymes (α-amylase and α-glucosidase) and ligands (3-oxolupenal and katononic acid) was followed by fluorescence quenching and molecular docking studies. 3-oxolupenal and katononic acid showed IC50 values of 46.2 μg/mL (101.6 µM) and 52.4 μg/mL (119.3 µM), respectively against the amylase inhibition. 3-oxolupenal (62.3 µg/mL or 141.9 μM) exhibited more potent inhibition against α-glucosidases compared to katononic acid (88.6 µg/mL or 194.8 μM). In terms of antioxidant activity, the relatively polar crude extract and n-butanol fraction showed the greatest DPPH and ABTS scavenging activity. However, the antioxidant activities of the purified compounds were in the low to moderate range. Molecular docking studies confirmed that 3-oxolupenal and katononic acid interacted strongly with the active site residues of both α-amylase and α-glucosidase. Fluorescence quenching results also suggest that 3-oxolupenal and katononic acid have a good affinity towards both α-amylase and α-glucosidase enzymes. This study provides preliminary data for the plant’s use in the treatment of type 2 diabetes mellitus.

Pentacyclic triterpenoids including the oleanane, ursane and lupane groups are widely distributed in many medicinal plants, such as Glycyrrhiza species, Gymnema species, Centella asiatica, Camellia sinensis, Crataegus species and Olea europaea, which are commonly used in traditional medicine for the treatment of diabetes and diabetic complications. A large number of bioactive pentacyclic triterpenoids, such as oleanolic acid, glycyrrhizin, glycyrrhetinic acid, ursolic acid, betulin, betulinic acid and lupeol have shown multiple biological activities with apparent effects on glucose absorption, glucose uptake, insulin secretion, diabetic vascular dysfunction, retinopathy and nephropathy. The versatility of the pentacyclic triterpenes provides a promising approach for diabetes management.

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Pomegranate has been documented for the management of diabetes in Unani and Chinese medicine. This study compared the effects of the extracts of different pomegranate parts, including juice, peels, seeds and flowers, on carbohydrate digestive enzymes (α-amylase and α-glucosidase) in vitro. The methanolic flower extract inhibited α-amylase and α-glucosidase, while the methanolic peel extract inhibited α-glucosidase selectively. The most active flower extract was subjected to water-ethyl acetate partition. The ethyl acetate fraction was more potent than the water fraction in inhibiting both enzymes. Gallic acid and ellagic acid also showed selective inhibition against α-glucosidase, and their presence in the ethyl acetate fraction was confirmed by HPLC-DAD and HPLC-HESI-MS. Our findings suggest that the inhibition of carbohydrate digestive enzymes and their phenolic content may contribute to the anti-hyperglycaemic effects of pomegranate flower and peel, and support their claims in diabetes.