Curcumin and Its Carbocyclic Analogs - Structure-Activity in Relation to Antioxidant and Selected Biological Properties

Sep 26, 2026

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Curcumin, the principal phenolic compound in turmeric (Curcuma longa L.), and fifteen novel carbocyclic analogs were evaluated for antioxidant and selected biological activities. Strong structure–activity relationships identified specific functional groups and carbon skeleton features as determinants of distinct biological profiles. Among tested compounds, derivatives 3e and 3d and the parent curcumin showed the highest free-radical scavenging and antioxidant capacity, with 3d also acting as the most potent ACE inhibitor.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages16

Reading Time40 min

AccessFree to download

Introduction

Curcumin and turmeric background

Oxidative stress, ROS/RNS, and antioxidant mechanisms

RAAS and ACE inhibition

Tyrosinase inhibition and anti-melanogenesis relevance

HIV and protease inhibition context

Molecules 2013, 18, 5389-5404; doi:10 .3390/molecules18055389 OPEN ACCESS molecules ISSN 1420-3049 [www.mdpi.com/journal/molecules](www.mdpi.com/journal/molecules) Article Curcumin and Its Carbocyclic Analogs: Structure-Activity in Relation to Antioxidant and Selected Biological Properties Khushwant S. Bhullar 1, Amitabh Jha 2, Dani Youssef 2,3 and H. P. Vasantha Rupasinghe 1,* 1 2 3 * Department of Environmental Sciences, Faculty of Agriculture, Dalhousie University, Truro, Nova Scotia, B2N 5E3, Canada Department of Chemistry, Acadia University, Wolfville, Nova Scotia, B4P 2R6, Canada Département des Science, Université Sainte Anne, Church Point, Nova Scotia, B0W 1M0, Canada Author to whom correspondence should be addressed; [E-Mail: vrupasinghe@dal.ca](E-Mail: vrupasinghe@dal.ca); Tel.: +1-902-8936623; Fax: +1-902-8931404 . Received: 9 April 2013; in revised form: 24 April 2013 / Accepted: 7 May 2013 / Published: 10 May 2013 Abstract: Curcumin is the major phenolic compound present in turmeric (Curcuma longa L.) . Curcumin and 15 novel analogs were investigated for their antioxidant and selected biological activities. Strong relationships between the structure and evaluated activity revealed that the compounds with specific functional groups and carbon skeleton had specific biological profiles. Among the compounds tested, the derivatives (E)-2-(3,4-dimethoxybenzylidene)-5-((E)-3-(3,4-dimethoxyphenyl)acryloyl)cyclopentanone (3e), and (E)-2-(4-hydroxy-3-methoxybenzylidene)-5-((E)-3-(4-hydroxy-3-methoxyphenyl)acryloyl) -cyclopentanone (3d) and the parent compound curcumin exhibited the strongest free radical scavenging and antioxidant capacity. Concerning the other biological activities studied the compound (E)-2-(4-hydroxy-3-methoxybenzylidene)-5-((E)-3-(4-hydroxy-3-methoxyphenyl)-acryloyl)cyclopentanone (3d) was the most potent angiotensin converting enzyme (ACE) inhibitor, while the derivatives (E)-2-(4-hydroxybenzylidene)-6-((E)-3-(4-hydroxyphenyl)acryloyl)cyclohexanone (2b), (E)-2-(3,4-dimethoxybenzylidene)-6-((E)-3-(3,4-dimethoxyphenyl)acryloyl)cyclohexanone (2e) and (E)-2-(3,4-dimethoxybenzylidene) - 5-((E)-3-(3,4-dimethoxyphenyl)acryloyl)cyclopentanone (3e) exhibited strong tyrosinase inhibition. Moreover, (E)-2-(3,4-dimethoxybenzylidene)-6-((E)-3-(3,4-dimethoxyphenyl) -acryloyl)cyclohexanone (2e) was also found to be the strongest human HIV-1 protease inhibitor in vitro among the tested compounds. Cytotoxicity studies using normal human lung cells revealed that the novel curcumin as well as its carbocyclic analogs are not toxic. Molecules 2013, 18 5390 Keywords: curcumin; antioxidant; tyrosinase; angiotensin converting enzyme; HIV 1. Introduction Curcumin [(1E,6E)-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione or diferuloylmethane, 1, Figure 1] is a naturally occurring phenolic compound derived from Curcuma longa L, commonly called turmeric [1] . Turmeric is an important medicinal ingredient in the Indian system of medicine called Ayurveda and is commonly used as a spice and food preservative. Extensive research during the last few decades has suggested the strong therapeutic and pharmacological potential ofcurcumin as antioxidant, antimutagenic and antibacterial agent [2] . Curcumin’s strong medicinal properties are also associated with reported anti-cancer [3] and neuroprotective characteristics [4] . Figure 1. Structures of curcumin and its 15 analogs. Reactive oxygen species (ROS) and free radicals are found to be pathological mediators in many diseases and disorders like diabetes, atherosclerosis, neurodegeneration, rheumatoid arthritis, human immunodeficiency virus (HIV) infection, ischemia and reperfusion injury and obstructive sleep apnea [5,6] . Curcumin exhibits its strong antioxidant activity via its ability to scavenge ROS, produced by catalytic activity of NAD(P)H oxidases and xanthine oxidases along with reactive nitrogen species (RNS) produce

FAQs

Which compounds showed the strongest free-radical scavenging and antioxidant capacity?

Derivatives (E)-2-(3,4-dimethoxybenzylidene)-5-((E)-3-(3,4-dimethoxyphenyl)acryloyl)cyclopentanone (3e), (E)-2-(4-hydroxy-3-methoxybenzylidene)-5-((E)-3-(4-hydroxy-3-methoxyphenyl)acryloyl)cyclopentanone (3d), and the parent compound curcumin exhibited the strongest free radical scavenging and antioxidant capacity.

Which compound was the most potent ACE inhibitor among the tested analogs?

The compound (E)-2-(4-hydroxy-3-methoxybenzylidene)-5-((E)-3-(4-hydroxy-3-methoxyphenyl)-acryloyl)cyclopentanone (3d) was identified as the most potent angiotensin converting enzyme (ACE) inhibitor.

What biological targets were assessed besides antioxidant activity?

Beyond antioxidant activity, the study assessed selected biological properties including tyrosinase inhibition, angiotensin converting enzyme (ACE) inhibition, and human HIV-1 protease inhibition, as well as cytotoxicity using normal human lung cells.

Sep 26, 2026

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