A Review of the Secondary Metabolites and Biological Activities of Tinospora crispa ( Menispermaceae )

Tinospora crispa Beumee, a herbaceous climber, has been widely used in traditional medicine for treating various ailments such as contusion, septicaemia, fever, fracture, scabies and other tropical ulcers. A wide range of secondary metabolites such as alkaloids, diterpenes, flavones, phenolics, and triterpenes have been isolated, some of which have also shown corresponding biological activities. The current review is an update on the reported pharmacological activities and phytochemical constituents of T. crispa.


INTRODUCTION
Tinospora crispa Beumee (Menispermaceae) [syn: T. tuberculata] or known as "akar patawali" or "akar seruntum" in Malaysia and "Borapet" in Thai and "Da ye ruan jin teng" in Chinese, is a herbaceous climbing plant that is widely distributed in South East Asia, particularly in Vietnam, Thailand, Malaysia, Indonesia and India [1][2][3][4][5].This medicinal herb has been used in the Thai traditional medicine due to its anti-pyretic, antidiabetic, anti-inflammatory, anti-malarial and health maintaining properties [6].It is also has been used in Chinese traditional medicine for the treatment of contusion, septicaemia, fever, fracture, scabies and other tropical ulcer related disorders [5,7].Oral administration of the decoction of the stem of the plant is claimed to possess anti-malarial and anti anthelmintic properties whereas decoction of the whole plant has been used as a postpartum remedy and also a traditional remedy for diabetes among the Malay community [3,[8][9][10][11][12].A poultice of fresh leaves is reported for treatment of wounds and itches [1,13].
The presence of two triterpenes, namely, cycloeucalenol and cycloeucalenone were reported for the first time from the chloroform extracts of the dried stems of T. crispa.Both of the isolated triterpenes further indicated mild cardiotonic effects, where cycloeucalenol showed slight increased in the right atrial contraction and initial reduction followed by 10 % of sustained reduction on the left atria of the rat in vitro meanwhile cycloeucalenone, showed slight change on the right and left atrial contraction [27].
Imphanban et al [28] isolated an aporphine alkaloid, namely, (-)-N-formylnornuciferine from the stems of T. crispa, which revealed in vitro cardiotonic activity.Synthesis of the mixture, (±)-N-formylnornuciferine, via palladium-catalyzed coupling reaction, indicated significant reduction in the force of contraction and the heart rate.
Bioassay guided fractionation of the n-butanol extract of the stems of T. crispa has resulted the isolation of five pharmacologically active compounds which were identified as salsolinol, adenosine, uridine, tyramine and higenamine, along with seven non-active compounds, namely, syringing, borapetoside A, B, D and E, adenine and litcubinine.The investigation of the pharmacologically active compounds on mechanisms of action on the blood pressure and heart rate in anesthetized, normal and reserpinized rats in vivo were carried out.The results of investigation further suggested that the cardiovascular responses of the anesthetized rats towards salsolinol, tyramine and higenamine were acted through the stimulation of the adrenoreceptors, whereby uridine and adenosine acted via the purinergic adenosine A 2 and P 2 receptors to decrease blood pressure with a transient decrease of heart rate followed by an increase [29].

Antifilarial activity
The aqueous extract of dried stems of T. crispa, assessed for in vitro antifilarial effects, has indicated moderate activity against the adult worms of subperiodic Brugia malayi after the aqueous extract of Xylocarpus granatum and dried leaves of Andrographis paniculata, whereby the value of relative movability values were used as a measure of the antifilarial activity [32].The aqueous extract of T. crispa was found to exhibit microfilaricidal activity which the microfilaricidal activity was investigated based upon direct observation of the microfilarial motility [33].

Antihyperglycaemic activity
The study of Noor and Ashcroft [34] indicated that the orally administrated extract of T. crispa exhibited significant antihyperglycaemic effect.The extract may consist of compounds which initiated the insulin secretion through the modulation of β-cell Ca 2+ concentration.Thus, it can be further used as an antidiabetic agent for the treatment of type II diabetes.

Anti-nitric oxide (Anti-NO) activity
The aqueous extract of T. crispa was found to suppress nitric oxide oxide production by lipopolysaccharide-stimulated murine macrophages.Significant inhibitory activity against the NO level and inducible NO synthase was showed by ethyl acetate layer when partitioned with the aqueous extract.Both subfraction of E-3 and N-trans-feruloyltyramine displayed strong anti-NO activity [35,36]

Antioxidant activity
Based on DPPH, FRAP and TBA tests, the aqueous crude extract of T. crispa stem was found to exhibit high antioxidant activity and its antioxidative potency is comparable to the established antioxidants, such as BHT and vitamin C [37,38].The antioxidant activity carried by Froemming [39] indicated that the methanol extract of T. crispa showed the highest antioxidant activity which was determined by measuring total flavonoid content, total phenolic content and DPPH free radical scavenging activity.

Antiparasitic activity
Rungruang & Boonmars [40] studied the in vivo antimalarial effect of the crude extract of T. crispa and the mice administrated of the extract with a dose of 80 mg/kg once a day were found to exhibit promising inhibitory activity against the parasite, Plasmodium yoelii.

Atherosclerosis inhibitory activity
The study conducted by Amom et al [41] revealed T. crispa stem aqueous extract delays the development of atherosclerosis by suppressing the total cholesterol, triglycerides, low density lipoprotein levels but showed a significant increased level of high density lipoprotein.

Thioacetamide-induced hepatotoxicity
Oral administration of ethanolic extract of T. crispa twice daily for 8 weeks at a dose of 100 mg/kg and 200 mg/kg was found to possess a significant effect on the thioacetamide-induced liver cirrhosis in rats [42].

Cardio-protective activity
The cardio-protective studies on the n-butanol extract of T. crispa demonstrated the presence of at least three different cardiovascular-active components which acted through (1) β 2adrenergic receptors to cause a decrease in blood pressure, and β 1 -and β 2 -adrenergic receptors to cause an increase in heart rate, (2) α-adrenergic receptors to cause an increase in blood pressure and heart rate, and (3) a nonadrenergic and noncholinergic pathway to cause a decrease in MAP and heart rate [43].

Central analgesic activity
The dried extract of stem of T. crispa exhibited promising central analgesic activity at a dosage of 666 mL [44].

Cytochrome inhibitory activities
Usia et al [45] studied the inhibitory effects of 30 indonesian medicinal plants against cytochrome P450 3A4 (CYP3A4) and CYP2D6 with a radiometric assay and suggested that T. crispa, showed inhibitory activity over 70% on the metabolism mediated by CYP3A4.Subehan et al [46] showed that among 30 other plants in an inhibitory assay of cytochrome P450 3A4 (CYP3A4) and CYP2D6 via erythromycin Ndemethylation and dextromethorphan Odemethylation activities in human liver microsomes that T. crispa, exhibited more than 30 % increase of CYP3A4 inhibition.

Hypoglycemic effects
Oral administration of T. crispa extract was found to display potent in vitro insulinotropic activity in the human and rat islets and HIT-T15 B cells [47].Sriyapai et al [48] examined the T. crispa dry powder for hypoglycemic effect on the patients with metabolic syndrome.Administrated of 250 mg T. crispa dry powder twice a day for 2 months was proven to decrease fasting blood glucose significantly from the baseline.The study by Noipha and Ninla-aesong [49] indicated that the extract of T. crispa enhances the glucose uptake by in L6 myotubes which was associated to the increased levels of GLUT1 transporter, AMPKα and PPARγ transcript.

CONCLUSION
A large number of secondary metabolites and biological activities have been reported from T. crispa; however, it would be valuable to conduct bioassay-guided phytochemical studies on this plant in order to isolate new biologically important secondary metabolites.

Figure 5 : 25 Figure 6 :
Figure 5: Compounds 19 -25 isolated three new diterpenoids, namely, 2-O-lactoylborapetoside B (28) (Figure 7), 6'-O-lactoylborapetoside B (29) and tinocrispol A (30), along with nine known diterpenoids, identified as borapetosides A-F, borapetols A and B and columbin from the ethanolic extract of T. crispa vines.Borapetosides A and C were found to lower the plasma glucose levels in normal and streptozotocin-induced type 1 diabetic mice upon examination on the in vivo hypoglycemic activities.

Figure 7 :
Figure 7: Compounds 28 -30 BIOLOGICAL ACTIVITIES AND FORMULATIONS Antibacterial activity The antibacterial studies conducted by Al-alusi et al. [31] has shown a promising antibacterial activity of T. crispa extracts against the Methicillin-resistant Staphylococcus aureus (MRSA) as compared to the control, vancomycin.