Inhibition of Helicobacter pylori growth and its cytotoxicity by 2-hydroxy 4-methoxy benzaldehyde of Decalepis hamiltonii (Wight & Arn); a new functional attribute.

Helicobacter pylori mediated gastric ulcer and cancers are common global problems since it was found to
colonize in w50% of gastric ulcer/cancer patients. Decalepis hamiltonii, (Asclepiadaceae family) extracts
have been depicted with medicinal properties supporting the traditional knowledge of health beneficial
attributes of D. hamiltonii. Previously we have shown that both aqueous as well as methanol extracts of
D. hamiltonii containing abundant phenolics with predominant levels (20e40% of total phenolics) of 2-
hydroxy-4-methoxy benzaldehyde (HMBA). Despite higher levels, HMBA contributed very little to the
antioxidant activity (<10%) when compared to other phenolic compounds in the extract. In the current
study we attempted to explore antimicrobial property, particularly anti-H. pylori activity, since traditional
users document D. hamiltonii as a fighter of microbial infections. HMBA was isolated from the roots of D.
hamiltonii by hydrodistillation and cold crystallization method; identified by HPLC and characterized using
ESI-MS and confirmed byNMR studies as a compound of molecular mass 152 Da. IsolatedHMBAwas found
to inhibit the growth of H. pylori, a potential ulcerogen in a dose dependent manner with MIC of w39 mg/
mL as apposed to that of amoxicillin (MIC e 26 mg/mL) for which H. pylori is susceptible. Results were
further substantiated by the lysis of H. pylori by electron microscopy and electrophoretic studies. Studies
on the mechanism of action indicated the counteracting effect of vacuolating toxin (VacA) of H. pylori
which otherwise would lead to host cell cytotoxicity. Further the increased binding ability of HMBA to DNA
and protein offered an impact on DNA protectivity and bioavailability. Results for the first time provide
a direct evidence for anti-microbial attribute of HMBA. Insignificant antioxidant attribute of HMBA also
reveals the anti-H. pylori activity via mechanisms other than antioxidative routes.