title: Discovery of arjunolic acid as a novel non-zinc binding carbonic anhydrase II inhibitor.
abstract: Elevated levels of carbonic anhydrase II (CA II) have been shown to be associated with cardiac hypertrophy and heart failure. Although arjunolic acid (AA) has a diverse range of therapeutic applications including cardio-protection, there have been no reports on the effect of AA on CA II. The present study describes for the first time, the novel zinc independent inhibition of CA II by AA. The molecular docking studies of AA indicated that the hydroxyl group at C2 of the A-ring, which hydrogen bonds with the catalytic site residues (His64, Asn62 and Asn67), along with the gem-dimethyl group at C20 of the E-ring, greatly influences the inhibitory activity, independent of the catalytic zinc, unlike the inhibition observed with most CA II inhibitors. Among the triterpenoids tested viz. arjunolic acid, arjunic acid, asiatic acid, oleanolic acid and ursolic acid, AA was the most potent in inhibiting CA II in vitro with an IC50 of 9μM. It was interesting to note, that in spite of exhibiting very little differences in their structures, these triterpenoids exhibited vast differences in their inhibitory activities, with IC50 values ranging from 9μM to as high as 333μM. Furthermore, AA also inhibited the cytosolic activity of CA in H9c2 cardiomyocytes, as reflected by the decrease in acidification of the intracellular pH (pHi). The decreased acidification reduced the intracellular calcium levels, which further prevented the mitochondrial membrane depolarization. Thus, these studies provide a better understanding for establishing the novel molecular mechanism involved in CA II inhibition by the non-zinc binding inhibitor AA.
authors.affiliation: Amrita School of Biotechnology, Amrita University, Amritapuri Campus, Clappana P.O., Kollam 690 525, Kerala, India.
authors.forename: Subhalakshmi
authors.initials: S
authors.lastname: Kalyanavenkataraman
authors.affiliation: Amrita School of Biotechnology, Amrita University, Amritapuri Campus, Clappana P.O., Kollam 690 525, Kerala, India.
authors.forename: Pandurangan
authors.initials: P
authors.lastname: Nanjan
authors.affiliation: Amrita School of Biotechnology, Amrita University, Amritapuri Campus, Clappana P.O., Kollam 690 525, Kerala, India.
authors.forename: Asoke
authors.initials: A
authors.lastname: Banerji
authors.affiliation: Amrita School of Biotechnology, Amrita University, Amritapuri Campus, Clappana P.O., Kollam 690 525, Kerala, India.
authors.forename: Bipin G
authors.initials: BG
authors.lastname: Nair
authors.affiliation: Amrita School of Biotechnology, Amrita University, Amritapuri Campus, Clappana P.O., Kollam 690 525, Kerala, India. Electronic address: ammasgeeta@gmail.com.
authors.forename: Geetha B
authors.initials: GB
authors.lastname: Kumar
mesh_terms: D000818:Animals; D024402:Carbonic Anhydrase II / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002257:Carbonic Anhydrase Inhibitors / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D055808:Drug Discovery; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D015394:Molecular Structure; D051381:Rats; D013329:Structure-Activity Relationship; D014315:Triterpenes / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D002257:Carbonic Anhydrase Inhibitors; D014315:Triterpenes; C061640:arjunolic acid; D024402:Carbonic Anhydrase II
keywords: Arjunolic acid; Carbonic anhydrase II; Non-zinc binding inhibitor