12 January - 20 June 2016

The Indian Long Pepper’s anti-cancer properties

A study, conducted by researchers from The University of Texas Southwestern Medical Center, Dallas, and published in the Journal of Biological Chemistry, suggests it has uncovered the chemical structure and processes which give the Indian Long Pepper anti-cancer properties.

A study, conducted by researchers from The University of Texas Southwestern Medical Center, Dallas, and published in the Journal of Biological Chemistry, suggests it has uncovered the chemical structure and processes which give the Indian Long Pepper anti-cancer properties.

Medicinal uses of the fruit of the Indian Long Pepper plant (piper longum) are said to date back thousands of years.  Previous studies have shown that a chemical derived from the fruit, piperlongumine (PL), causes apoptosis (programmed cell death) in cancer cell lines but not in non-cancer cells. PL has also been shown to have anti-tumour activity against a range of cancers including prostate, breast and lung cancer.

The authors of the study wanted to investigate the mechanism by which PL causes these effects against cancer cells and tumours. Using x-ray crystallography, Harshbarger et al. found that PL is hydrolysed to a trimethoxycinnamic acid which they termed hydrolysed PL (hPL), and that it was hPL which seems to be the active drug. hPL appears to inhibit the catalytic effect of glutathione S-transferase pi 1 (GSTP1), an enzyme which is often overexpressed in cancerous tumours. Harshbarger et al. also found that while in vitro, hPL inhibited the activity of GSTP1, when used on cancer cell lines directly, it did not have “significant anti-proliferative effects” unlike PL. They suggest this indicates that hPL is not membrane permeable and thus that hydrolysis of PL “occurs only after passage into cells”. GSTP1 belongs to a family of proteins called GSTs and while other GST inhibitors have been found and shown to have anti-tumour properties, these have generally been too toxic to consider using in humans.

In conclusion, Harshbarger et al. state that they have provided the “first structural model” for interactions between PL and GSTP1. They note that PL’s effect occurs only after its hydrolysis within the cell, to hPL, and reiterate that it is the hPL that inhibits the enzymatic activity of GSTP1. They state that they consider PL to be a prodrug (a biologically inactive compound which can be metabolized in the body to produce a drug) and that their results might be able to “form the basis for a structure-guided design approach” for novel PL type compounds which could be used as “chemotherapeutic agents”.

Dr Kenneth Westover, the corresponding author of the study is quoted in a press release as saying that the study “illustrates the importance of examining and re-examining our theories. In this case, we learned something fundamentally new about a 3000-year-old medical claim using modern science”.  Westover added that “this research is a spectacular demonstration of the power of x-ray crystallography”.

RSSL's can carry out tests on chilli pepper pungency by HPLC according to the ASTA Method. RSSL can also provide analysis of the red coloured compounds characteristic of capsicums of all kinds. To find out more please contact Customer Services telephone 0118 918 4076 or e-mail enquiries@rssl.com

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