Biological Activities of Betulin and Betulinic Acid
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Betulin is the one of the premier pure, crystalline natural product obtained from plants through extraction and sublimation of birch bark (Lowitz 1788). Betulin and betulinic acid are closely related to each other, often found together in varying amount in different plant species when extracted by different solvents . Early anti septic property of betulin and its use become famous to be used in plaster for sterilization of cuts and wound .Studies indicated that betulin carry wound healing, cholesterol lowering activity, hepato-protecteive, anti-bacterial, anti-leishmenial, anti-viral, anti-cancer activities (Wheeler1899). Due to the high mutagenecity of HIV-1 and cancers cells in order to improve the biological activity of betulin and its derivatives various strategies were applied and still going on (Csuk, 2014), here we are presenting a coverage of the betulin, betulinic acid and its derivatives with their biological activity.
Study carried on lung injury showed that betulinic acid protects sepsis induced lung injury against inflammation and indicated it as a potential regulator of the inflammation. In another study the positive effect on the acute lung injury cured by betulinic acid. The septic lung injury is generally characterized by the severe oxidative stress response, in addition to available treatment new methods are required to improve further clinical outcomes (Lingaraju et al., 2015). Lingaraju and coworkers found the effect of betulinic acid using cecal ligation and puncture model on oxidative lung injury. They treated two groups of mice with different concentration of betulinic acid, further their lung and plasma samples were collected for analysis by sacrificing the mice at 18hr. of surgery. They concluded increased antioxidants level in blood that lead to reduced lung injury in mice. The role of betulinic acid induces programmed death of human red blood cells (erythroptosis) was reported, which is mediated through membrane permeabilization and calcium ion load (Gao et al.2014). Afzal and his group (Afzal et al. 2014) studied on the hypothyroidism in female albino rate for 2 months by giving them standard drug propyl thio uracil (PTU) for the induction of lower level of TSH for two months. Later on the mice were treated with standard thyroxin at a dose of 10μg/kg and the test drug betulinic acid at a dose of 20μg/kg of body weight. Finally after the two months study betulinic acid treated animals showed marked improvement in the follicle integrity that showed betulinic acid has protective activity against hypothyroidism. Two groups of semi synthetic derivatives of betulin (BT01 to BT09) and betulinic acid (AB10 to AB16) were synthesized respectively which has shown antileishmanial combined-therapy with miltefosine (Sousa et al.2014). Leishmaniasis was previously treated by miltefosine, amphotericin B, pentavalent antimony compounds, pentamidine etc. but due to their toxicity and biological resistance new therapeutics as betulin and betulinic acid derivatives are new avenues for its treatment. Accordingly, it is important to continue the search for new effective and less toxic treatments. Effects on the cell cycle, apoptosis / necrosis events, morphology and DNA integrity with isobologram method were used for a comparative study in between miltefosine with some of the derivative synthesized during the study. The AB13 (28-(1H-imidazole-1-yl)-3,28-dioxo-lup-1,20(29)-dien-2-yl-1H-imidazole-1-carboxylate) and BT06 (3β-Hydroxy-(20R)-lupan-29-oxo-28-yl-1H-imidazole-1-carboxylate) derivatives were found to be the most active, with IC50 values of 25.8 µM, and 50.8 µM respectively. Synergistic interactions were observed between these two compounds and miltefosine. Significant morphological changes were observed using AB13, while both derivatives (AB13 and BT06) produced anti-proliferative activity through cell cycle arrest at the G0/G1 phase. Neither of these derivatives induced significant apoptosis /necrosis, as indicated by phosphatidylserine externalization and DNA fragmentation assays. Not only that, neither of the derivatives induced death in macrophage cell lines. Thus, they do not present any potential risk of toxicity for the host cells.
This study identified the betulin derivative BT06 and the betulinic acid derivative AB13 as promising molecules in the development of new alternative therapies for leishmaniasis, including those involving combined-therapy with miltefosine. The solubility of betulin and its derivatives has been the most significant issue in drug development from these hydrophobic molecules . To overcome this problem nano-emulsion gels of betulinic acid were formulated(Bag and Dash 2011). They tried 20 organic solvents as well aqueous alcohol mixture to synthesize renewable nano-sized 6-6-6-6-5 pentacyclic triterpenic acid . They confirmed their results of increased hydro solubility as they found nano and micrometer length fibers using atomic force microscopy as well electron microscopy. Role of betulinic acid in manipulating the significant actions and role of xenobiotic and antioxidative enzymes in cancer initiation and proliferation were studied (Kaur and Arora 2013) . They studied on the interactions of betulinic acid on Sprague Dawley female rats with xenobiotic metabolizing enzymes including cytochrome b5, P420, P450, NADPH cytochrome P450 reductase, and NADH cytochrome b5 reductase (mixed function oxidases ), GST, DT-diaphorase, γ-glutamyl transpeptidase (phase II enzymes), alone as well as in the presence of 7,12 dimethylbenzanthracene(DMBA). The reduction in glutathione content and protein content was considered in the study to get the effect of betulinic acid. They observed the lower level of mixed function oxidases those are responsible for the conversion of carcinogen to electrophile and further increase in phase II enzymes which participated in the removal of electrophiles by sulfation or conjugation under betulinic acid treatment . Also reported that betulinic acid effectively removed or neutralized the reactive species by the action of phase II enzymes and such an effect was demonstrated from the specific activities of antioxidative enzymes which were found to be lower as compared to positive control (DMBA-treated group) and in some cases even that of untreated control. They also found a pronounced effect of betulinic acid in protecting the animals from lipid peroxidation as evident from the reduced levels of TBARS, conjugated diene, and lipid hydroperoxide formation. Inhibition of SREBP1 activity through AMPK-mTOR-SREBP signaling pathway using betulinic acid was studied (Kim et al.2013) . Insulin-resistant HepG2 cells, primary rat hepatocytes and liver tissue from high-fat fed ICR mice were used to get insight of the mechanism responsible for anti fatty liver effect . Accumulations of triglyceride are the indication of fat deposition that was analyzed by “Oil Red O staining”, which suppression was reported by betulinic acid. Calcium-calmodulin dependent protein kinase kinase (CAMKK) and AMP-activated protein kinase (AMPK) both were activated by betulinic acid while on the other hand the mammalian target of rapamycin (mTOR), protein levels of sterol regulatory element-binding protein 1 (SREBP1), and S6 kinase (S6K) were all reduced when hepatocytes were treated with betulinic acid for up to 24 hours. Reduced lipogenesis leading to low lipid accumulation, nuclear translocation and repressed SREBP1 target gene expression in HepG2 cells and primary hepatocytes, suppression of SREBP1 mRNA expression and activation of AMPK via phosphorylation through betulinic acid were also highlighted in the study. Overall they suggested that betulinic acid could be promising molecule effectively ameliorating intracellular lipid accumulation in liver cells preventing fatty liver diseases. Reduction in skin hyper-pigmentation using betuinic acid from Vitis amurensis root and its anti-melanogenic effect and precise mechanism underlying the anti-melanogenic activity of betulinic acid in B16F10 cells were investigated (Jin et al. (2014). Betulinic acid significantly reduced 3-isobutyl-1-methylxanthine (IBMX)-induced melanin synthesis by inhibiting tyrosinase, tyrosinase related protein (TRP)-1, and TRP-2 expression through the modulation of their corresponding transcription factors in B16F10 cells. In addition, phosphorylation of mitogen-activated protein kinase (MAPK)/extra cellular regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K) involved in the melanogenesis processes, were ameliorated by betulinic acid treatment. Specific inhibitors were used, PD98059 (for MEK/ERK) and LY294002 (for PI3K/Akt respectively) to confirm the role of MEK/ERK and PI3K/Akt signaling pathway in the melanogenesis. Consequently, betulinic acid inhibited melanin production by tyrosinase, TRP-1, and TRP-2 inhibition through the regulation of CREB and MITF, which was accompanied with MEK/ERK and PI3K/Akt inactivation in IBMX-stimulated B16F10 cells. Finally these results expressed a novel molecular function of betulinic acid melanogenesis, which in turn enhances our understanding on the application of cosmetic therapy for reducing. Investigation were done on betulinic acid mediated fat mobilization by enhancing the level of lipolysis in adipose tissue that showed the antiobesity properties of betulinic acid with their possible mechanisms (Kim et al.2012). The lipolytic effects of betulinic acid were assayed in rat adipose tissues with inhibition of anti-lipase function and pancreatic lipase activity of betulinic acid in vitro which lead to prevent the elevation of plasma triacylglycerol levels, after oral administration of a lipid emulsion to rats where activity of cAMP-dependent phosphodiesterase was also measured. Betulinic acid inhibited pancreatic lipase activity in a dose-dependent manner at concentrations of 1.5-100â€‰µM (ICâ‚…â‚€ value of 21.10â€‰µM) prevented the elevation of plasma triacylglycerol level after 2 hours of oral administration of the lipid emulsion at a dose of 100â€‰mg/kg concluded the strong lipolytic effect of betulinic acid which was mediated by cAMP-dependent phosphodiesterase inhibition. Betulinic acid exerted antiobesity effects by directly inhibiting pancreatic lipase, that can prevent the absorption of lipid from the small intestine. Recent studies on the chemical as well biological synthesis of the betulinic acid derivatives , they used fungi in combination with plant tissue culture of carrot and found that the most active derivative as , 3-(2,4-dinitrophenyl)hydrazono-lup-(20R)-29-oxolupan-28-oic acid, showed IC50values between 1.76 and 2.51μM against five human cancer cell lines (Baratto et al. 2013). The most selective, 3-hydroxy-20-(2, 4-dinitrophenyl) hydrazono-29-norlupan-28-oic acid, was five to seven times more selective for cancer cells when compared to fibroblasts. The cell cycle studies and apoptosis induction, with high cytotoxicity and selectivity on the tumour cell shown the efficacy of the transformed molecule. The design and synthesis of seco derivtives from the alteration in the “A” ring of betulinic acid were carried (Hsin-Yi Hung 2014). A group of compounds were synthesized and their enhanced chemopreventive ability in vitro short term induced assays were done in Raji cells, C28 modified analogs shown significant activation. One of the modified derivative was found to shown 100% inhibition of EBV-EA at 1×103molratio/TPA ,73.4%, 35.9%, and 8.4% inhibition at 5×102, 1×102, and10molratio/TPA, respectively, comparable with curcumin at high concentration. In an investigation the role of betulinic acid co-regulation with vitamin D3,was reported that showed that betulinic acid improves insulin secretion with increasing glycogen content and glucose uptake in muscle tissue(Castro et al.2014). It was also reported that betulinic acid enhances the GLUT4 immunocontent and its translocation was supported by GLUT4 itself as well it does not cause hyper-calcemia that is very significant from the drug discovery perspective. In search of safe and natural treatment of obesity betulinic acid was tried as anti-obese drug on swiss albino male mice fed with high fat diet. Betulinic acid was extracted from ethanolic root extract of Clusia nemorosa (Rao et al. 2009).They treated mice at 50mg/kg body weight with control where they found significant control on the
The therapeutic potential of betulinic acid on bone metastases and skeletal complications in breast cancer patients were investigated (Park et al.2014). They suggested the protective and therapeutic potential of betulinic acid on cancer-associated bone diseases. This is the first report indicating effect of betulinic acid on breast cancer cells, osteoblastic cells, and osteoclasts in the vicious cycle of osteolytic bone metastasis. Betulinic acid reduced cell viability and the production of parathyroid hormone-related protein (PTHrP), a major osteolytic factor, in MDA-MB-231 human metastatic breast cancer cells stimulated with or without tumor growth factor-β. An increase in the receptor activator of nuclear factor-kappa B ligand (RANKL) / osteoprotegerin ratio was blocked by betulinic acid through down regulating RANKL protein expression in PTHrP-treated human osteoblastic cells. Not only that the inhibition of RANKL-induced osteoclastogenesis in murine bone marrow macrophages and decreased the production of resorbed area in plates with a bone biomimetic synthetic surface by suppressing the secretion of matrix metalloproteinase (MMP)-2, MMP-9, and cathepsin K in RANKL-induced osteoclasts was observed by betulinic acid. Furthermore, oral administration of betulinic acid inhibited bone loss in mice intra-tibially inoculated with breast cancer cells and in ovariectomized mice causing estrogen deprivation, as supported by the restored bone morphometric parameters and serum bone turnover markers. Taken together, these findings suggest that betulinic acid may have the potential to prevent bone loss in patients with bone metastases and cancer treatment-induced estrogen deficiency. A pioneer study on athymic nude mice, bearing MCF-7 breast adenocarcinoma xenografts was taken as in vitro cytotoxic and in vivo anti-tumor model (Damle et al. 2013). The antitumour activity of betulinic acid was studied at 50 and100 mg/kg body weights, whereas cytotoxic activity of MCF-7 cells with IC50 value of 13.5µg/ml was studied by MTT assay. Betulinic acid treatment shown significant reduction in tumour size of 77 and 52% tumour size (100 and 50 mg/kg body weight respectively) in addition decreased angiogenesis, proliferation and invasion in betulinic acid treated mice were also highlighted through histopathological studies. Through topomer CoMFA , some 35 derivatives of betulinic acid were prepared and tested against HT29 human colon cancer cells (Ding et al.2013) . The contour maps showed that bulky and electron-donating groups would be favorable for activity at the C-28 position, and a moderately bulky and electron-withdrawing group near the C-3 position would improve this activity. Few of the betulin derivativeswere designed and synthesized as per the modeling result, while groups such as maleyl, phthalyl, and hexahydrophthalyl (bulky electronegative groups) were directly introduced at the C-28 position. They also found consistency with predicted and actual IC50 value of the given analogsagainst HT29 cells, proving that the present topomer CoMFA model is successful and that it could potentially forward the synthesis of newbetulinic acidderivativeswith high anti-cancer activity. Five tumour cell lines were tested against three newly synthesized derivatives where 28-O-hexahydrophthalyl betulin shown the greatest anti-cancer activities and its ICâ‚…â‚€ values were lower than other tumour cell line except DU145.In an investigation Prunella vulgaris was used for betulinic acid and ursolic acid extraction those were responsible for the anti-estrogenic effects, suggested their potential application against estrogen-dependent tumors (Kim et al. 2014).In this study Prunella vulgaris constituents were isolated and tested their individual anti-estrogenic effects. Betulinic acids, ursolic acid, Rosmarinic acid, caffeic acid, oleanolic acid, hyperoside, rutin, were isolated from the flower stalks of P. vulgaris var. lilacina Nakai (Labiatae) which showed anti-estrogenic effects as a decreased level in the mRNA of GREB1,revealed significant anti-estrogenic effects of betulinic acid and ursolic acid, on estrogen receptors .They also demonstrated the
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