Case Study: Herbal Viagra

Any herbal product has the potential to be named as herbal Viagra and it can be advertised as treating erectile dysfunction. The name ‘ herbal Viagra ’ comes from the brand name Viagra which is manufactured by the drug company Pfizer. (Rzepa, H.S. , 1998). There are many analogues of sildenafil,tadalfil and vardenafil which are said to be adulterated in herbal viagra products. The first sildenafil analogue found in literature was homosildenafil ( M.H. Shin, M.K. Hong, W.S. Kim, Y.J. Lee, Y.C. Jeoung , 2003). Then, 2 more analogues of sildenafil disclosed are hydroxy-homosildenafil (C.L. Mei, C.L. Yi, H.L. Jer, J. , 2006) and acetildenafil ( L. Blok-Tip, B. Zomer, F. Bakker, K.D. Hartog, M. Hamzink, J. Ten Hove, M. Vredenbregt, D. De Kaste …show more content…
Sildenafil and many of its analogues can be prepared in two steps from a half-product called Sildenafil Intermediate B by using the synthetic approach as disclosed in the Pfizer patents .( A.S. Bell, D. Brown, N.K. Terrett , 1991; A.S. Bell, N.K. Terrett ,1992; P. Ellis, N.K. Terrett , 1994)As patent literature shows that for a PDE-5inhibitors, there are few structural requirements at the C16 position, providing hundreds of chances to numbers of analogue. A change in reagents early in the synthesis is needed in analogues with variations at N3 or C19. In 2002, claim of intellectual property on thio-analogues was published in patent literature. ( D.H. Kim, J.H. Kim, K.I. Choi, Y. Kim, G. Nam, J.H. Seo, 2002) The claim is essentially a copy of the Pfizer patent but with the C- O bond exchanged for C- S bond. Thio-sildenafil and its thio-analogues are not legally registered but identified as adulterants. A sildenafil analogue regularly identified as an adulterant is aildenafil .( J.C. Reepmeyer, J.T. Woodruff, D.A. d’Avignon , 2007; K.P. Deng, Z.Y. Luo, Y. Lei , 2011) Liu et al. claims the intellectual property of aildenafil . (B. Liu, 2005; Z.J. He, K. Zhang, J. Jin, N.C. Li, Y.Q. Na, W.J. Bai, X.F. Wang, J.C. Zhu, H. Jiang, R.P. Yuan, B.F. Hong, T. Song, Y. Yang, D.X. Dai, 2006 ; J. Wang, Y. Jiang, Y. Wang, X. Zhao, Y. Cui, J. Gu, 2007) In 2007, intellectual property which is …show more content…
4 h) .( H. Porst, H. Padma-Nathan, F. Giuliano, G. Anglin, L. Varanese, R. Rosen ,2003; H. Hedelin, P. Stroberg ,2005) It therefore extends the range of chance for the user to have sex.. Known analogues of tadalafil mostly have a variation at the N-atom of the amide. Variations at that position are introduced in the final step which is shown in patent