Antimicrobial activity of wax and hexane extracts from Citrus spp. peels

Abstract

Antibacterial and antifungal properties of wax and hexane extracts of Citrus spp. peels were tested using bioautographic and microdilution techniques against three plant pathogenic fungi (Penicillium digitatum, Curvularia sp., and Colletotrichum sp.), two human pathogens (Trichophyton mentagrophytes and Microsporum canis), and two opportunistic bacteria (Escherichia coli and Staphylococcus aureus). Two polymethoxylated flavonoids and a coumarin derivative, were isolated and identified from peel extracts, which presented antimicrobial activity especially against M. canis and T. mentagrophytes: 4 ',5,6,7,8-pentamethoxyflavone (tangeritin) and 3',4',5,6,7,8-hexamethoxyflavone (nobiletin) from C. reticulata; and 6,7-dimethoxycoumarin (also known as escoparone, scoparone or scoparin) from C. limon.Key words: polymethoxylated flavonoids -antibiosis -pathogens -fungi -bacteria Citrus spp. are considered an important source of polymethoxylated flavonoids (PMF), a class of secondary plant metabolites (Afek et al. 1986). PMF's are generally found bound to sugar moieties (glycosides) or in exceptional circumstances as free aglycones (Robards et al. 1997). They are often used to establish phylogenetic relationships among plants (Mizuno et al. 2001). However, flavonoids are known to have physiological effects on other organisms. They have been shown to reduce erythrocyte aggregation and sedimentation rates in human blood (Robbins 1976), as well as to exhibit antiviral (Brinkworth et al. 2002), antimutagenic (Iwasse et al. 2001), and antimicrobial properties (Afek et al. 1986, Cushinie & Lamb 2005. Some studies have indicated that foods containing high amounts of flavonoids may reduce the risk of heart diseases, due to their antioxidant properties (Young et al. 1999, Arts et al. 2001, Tripoli et al. 2007).Studies of the antimicrobial activities of flavonoids have become important because of the increasing occurrence of opportunistic systemic mycosis, as well as the rising prevalence of drug resistance in human pathogenic bacteria (Afek et al. 1986). Drug-resistant bacteria and fungi have complicated the treatment of infectious diseases in immunocompromised AIDS and cancer patients. The evolution of multiple drug resistant human pathogenic microorganisms, has driven the search for new sources of antimicrobial substances, including plant metabolites (Nostro et al. 2002).The dramatic increase in the resistance of plant pathogens to chemical fungicides has led to the use of repeated applications of chemical fungicides to control plant diseases. As a consequence, public concern has increased the demand for safer and less environmentally harmful agrochemicals (Wedge & Nagle 2000). New antifungal and antibacterial agents are necessary to address this situation.PMFs with their lipophylic properties, are usually present in vacuoles or in the wax cuticle of plants. Several studies have detected their presence in the wax epicuticular layer on plants where they play a role in protecting these regions against UV radiation and microbial ...

Proteome and transcriptome profile analysis reveals regulatory and stress-responsive networks in the russet fruit skin of sand pear

“…10). Triterpenoids have a potential role in the protection against pathogens and pests due to their antimicrobial activity [35][36][37] . Triterpene caffeates with antiinflammatory activities have been identified in pear and apple with preferential expression in russet skin 36 .…”

Natural Products for Cancer-Targeted Therapy: Citrus Flavonoids as Potent Chemopreventive Agents

“…Nobiletin, flavonoid obtained from C. reticulata peels, blocked carcinogenesis on DMBA-induced mice's skin (Murakami et al, 2000). Further study was then conducted via in silico study on nobiletin and tangeretin, two flavonoids contained in C. reticulata peels (Johann et al, 2007). Those two citrus flavonoids do not bind c-Src (N-Ras' upstream) stronger that ATP and imatinib do, respectively, while imatinib-c-Src has more stable binding compared to that is on ATP-c-Src Putri et al, 2008).…”

An unusual plant triterpene synthase with predominant α‐amyrin‐producing activity identified by characterizing oxidosqualene cyclases from Malus × domestica

“…Their biological role has not been clearly established; however, a potential antimicrobial activity of their glycosylated derivatives (saponins) suggests a role in protection against pathogens and pests [1–4]. Triterpenoids display a wide range of important medicinal activities, including anti‐inflammatory [5,6], antitumour [7], anti‐leukaemic [8], anti‐HIV [9,10], antifungal [2,11] and antidiabetic [12] activities [13]. Over the years, these promising therapeutic properties have resulted in a great deal of interest in the triterpenoids, and well over 1000 of these natural compounds have been isolated from plants.…”