Antihyperglycaemic flavonoids from Syzygium samarangense (Blume) Merr. and Perry

2',4'-Dihydroxy-3',5'-dimethyl-6'-methoxychalcone 1, its isomeric flavanone 5-O-methyl-4'-desmethoxymatteucinol 2 and 2'4'-dihydroxy-6'-methoxy-3'-methylchalcone 3 were isolated from the leaves of S. samarangense using a bioassay-directed scheme. In an oral glucose tolerance test, at a dosage of 1.0 mg/20 g mouse, 1 and 2 significantly (alpha = 0.05) lowered the blood glucose levels (BGLs) in glucose-hyperglycaemic mice when administered 15 min after a glucose load. When co-administered with glucose, only 1 showed a significant lowering of BGLs 45 min after its oral administration. When administered 15 min before glucose, none of the flavonoids showed a positive effect. Only 1 decreased significantly, at alpha = 0.05, the BGLs of alloxan-diabetic mice at t = 90-150 min.     

Effect of Water Extracts from Edible Myrtaceae Plants on Uptake of 2‐(n‐(7‐nitrobenz‐2‐oxa‐1,3‐diazol‐4‐yl)amino)‐2‐deoxyglucose in TNF‐α‐Treated FL83B Mouse Hepatocytes

This study investigated the glucose uptake activity of the water extracts from the leaves and fruit of edible Myrtaceae plants, including guava (Psidium guajava Linn.), wax apples [Syzygium samarangense (Blume) Merr. and L.M. Perry], Pu‐Tau [Syzygium jambo (L.) Alston], and Kan‐Shi Pu‐Tau (Syzygium cumini Linn.) in FL83B mouse hepatocytes. The fluorescent dye 2‐(n ‐(7‐nitrobenz‐2‐oxa‐1,3‐diazol‐4‐yl)amino)‐2‐deoxyglucose was used to estimate the uptake ability of the cells. Glucose uptake test showed that pink wax apple fruit extract (PWFE) exhibits the highest glucose uptake activity, at an increment of 21% in the insulin‐resistant FL83B mouse hepatocytes as compared with the TNF‐α‐treated control group. Vescalagin was isolated using column chromatography of PWFE. This compound, at the concentration of 6.25 µg/mL, exhibits the same glucose uptake improvement in insulin‐resistant cells as PWFE at a 100‐µg/mL dose. We postulate that vescalagin is an active component in PWFE that may alleviate the insulin resistance in mouse hepatocytes. Copyright © 2012 John Wiley & Sons, Ltd.     

Antimicrobial activity of bark extracts of Syzygium jambos (L.) alston (Myrtaceae)

Syzygium jambos (L.) Alston (Myrtaceae) is a widespread medicinal plant traditionally used in sub-Saharan Africa to treat infectious diseases. Acetone and aqueous extracts from the bark of S. jambos were tested for antimicrobial activity in vitro by the agar dilution method in petri dishes. Both extracts showed some activity against the tested micro-organisms. They proved to be particularly effective on Staphylococcus aureus, Yersinia enterocolitica and coagulase negative staphylococci among which Staphylococcus hominis, Staphylococcus cohnii and Staphylococcus warneri. These properties seem to be related to the high tannin content of S. jambos extracts (77 and 83% for the aqueous and acetone extracts, respectively, determined according to the European Pharmacopoeia method) which were generally more active than Hamamelis virginiana, Krameria triandra, Alchemilla vulgaris and Rubus fruticosus extracts containing 48, 44, 46 and 28% tannins, respectively. Furthermore, elimination of tannins totally suppressed these antimicrobial activities.     

Effects of Syzygium cordatum (Hochst.) [Myrtaceae] leaf extract on plasma glucose and hepatic glycogen in streptozotocin-induced diabetic rats

The present study investigates the hypoglycaemic effect of Syzygium cordatum (Hochst.) [Myrtaceae] leaf extract in non-diabetic and streptozotocin (STZ)-induced diabetic rats. Oral glucose tolerance tests (OGGT) were conducted in non-diabetic and STZ-diabetic rats using orally administered glucose (1.4 g 100 g(-1) body weight) followed by either the leaf extract (6 mg 100 g(-1) body weight) or subcutaneous (sc) injection of metformin (50 mg 100 g(-1)). Weekly plasma glucose and terminal hepatic glycogen concentrations were recorded in control STZ-diabetic rats and diabetic rats orally treated with the leaf extract once every third day for 4 weeks. Administration of the leaf extract decreased plasma glucose from 7.7+/-0.9 mmol l(-1) to 3.7+/-0.6 mmol l(-1) (n = 6), and 21.1+/-2.2 mmol l(-1) to 12.5+/-1.8 mmol l(-1) (n = 7) by 2 1/2 h in non-diabetic and STZ-diabetic rats, respectively. OGTT data in metformin-treated rats were similar at the corresponding time in all groups, except for significant blood glucose reduction by the drug in non-diabetic rats between 1 and 1 1/2 h after treatment. Oral administration of the extract did not affect plasma glucose concentration in STZ-diabetic rats after 4 weeks, although it significantly increased hepatic glycogen content by comparison with untreated STZ-diabetic rats (28+/-5 mg 100 g(-1) body weight, n = 7, versus 16+/-3 mg 100 g(-1) body weight, n = 6). We conclude that Syzygium cordatum leaf extract contains compounds that could be effective in mild diabetes mellitus or in cases of glucose tolerance impairment. The possible mechanism(s) involved in the short-term hypoglycaemic effect of the extract could not be established by the current study.     

RP—HPLC测定海南产胡椒根中胡椒碱的含量

目的：采用RP—HPLC首次建立了海南产胡椒根中胡椒碱的含量测定方法。方法：分析柱采用Eclipse XDB-C18（4．6＊ 150mm,5um）色谱柱,流动相为甲醇-水（V：V=75：25）;流速：1．0mL／min;检测波长：343nm。结果：胡椒碱的线性范围分别为0．1～1．0mg／ml;相关系数为0．9997。平均加样回收率分别为9．4％,98．7％,100．9％;RSD为2．1％,1．6％,2．3％（n=9）。结论：采用RP—HPLC同时测定海南产胡椒根中胡椒碱的含量,该法简单、可靠,可作为控制胡椒根药材质量的参考标准。     

The anti-diarrhoeal properties of Breonadia salicina, Syzygium cordatum and Ozoroa sphaerocarpa when used in combination in Swazi traditional medicine

Aim of the study

The aim of the study was to determine in vitro activity of the bark of Ozoroa sphaerocarpa R. Fern & A. Fern (Anacardiaceae), Breonadia salicina (Vahl) Hepper & J.I.R. Wood (Rubiaceae) and Syzygium cordatum Hochst ex C Krauss (Myrtaceae) against a diarrhoea-causing pathogen, Escherichia coli; as well as the pharmacological interactions present in their combination.

Materials and methods

In consultation with traditional healers, the plants were collected from the wild, dried and extracted with dichloromethane:methanol (1:1). Thereafter, antimicrobial activity of the individual plants and their different combinations was tested using a common diarrhoea pathogen, Escherichia coli by employing the minimum inhibitory concentration assay.

Results

Ozoroa sphaerocarpa was the most potent inhibitor of antimicrobial growth (MIC value of 1.2 mg/ml), followed by Syzygium cordatum (MIC value of 1.44 mgl/ml) and lastly Breonadia salicina (MIC value of 10.89 mg/ml). The combination between Syzygium cordatum and Ozoroa sphaerocarpa gave the strongest synergistic interaction (MIC value of 0.33 mg/ml); whilst that between Syzygium cordatum and Breonadia salicina was mildly synergistic (MIC value of 1.00 mg/ml). The triple combination (1:1:1) was also very effective in inhibiting microbial growth (MIC value of 0.44 mg/ml). The combined effect of these plants on toxicity was predominantly synergistic except for the combination of Ozoroa sphaerocarpa and Syzygium cordatum which was predominantly antagonistic (ΣFIC value of 1.48 ± 0.25). The triple combination had a favourable toxicity profile with an IC₅₀ value of 155.76 ± 11.86 μg/ml.

Conclusion

This study supports the rationale by traditional healers to use the bark of Syzygium cordatum, Breonadia salicina and Ozoroa sphaerocarpa in combination for the treatment of diarrhoea.     

Induction of apoptosis in HepG2 cells by solanine and Bcl-2 protein

The nightshade (Solanum nigrum Linn.) has been widely used in Chinese traditional medicine as a remedy for the treatment of digestive system cancer. The anti-tumor activity of solanine, a steroid alkaloid isolated from the nightshade has been demonstrated. To observe the effect of anti-tumor and mechanism of solanine. The MTT assay was used to evaluate the IC(50) on the three digestive system tumor cell lines. The effect on the morphology was observed with a laser confocal microscopy; the rate of apoptosis and the cell cycle were measured using flow cytometry (FCM); the expression of Bcl-2 protein was measured by Western blot. The results show that the IC(50) for HepG(2), SGC-7901, and LS-174 were 14.47, >50, and >50 microg/ml, respectively; the morphology of cells in the negative control was normal; for the treated groups, typical signs for apoptosis were found. The rate of apoptosis in HepG(2) cells induced by solanine was found to be 6.0, 14.4, 17.3, 18.9, and 32.2%, respectively. Observation of the cell cycle showed that cells in the G(2)/M phases disappeared while the number of cells in the S phase increased significantly for treated groups. Western blot showed that solanine decreased the expression of Bcl-2 protein. Therefore, the target of solanine in inducing apoptosis in HepG(2) cells seems to be mediated by the inhibition in the expression of Bcl-2 protein.