رابطه فعاليتهاي ضد ميكروبي روغنهاي اسانسي Mentha spicata L. و Chenopodium ambrosioides L. با خواص آنتي‌اكسيداني و راديكال‌زدايي آنها

اسانس گياهان پونه (Mentha spicata L.) و سلمك معطر (Chenopodium ambrosioides L.)، با روش تقطير با بخار آب استخراج و تركيبهاي آنها با دستگاههاي گاز كروماتوگرافي (GC) و گاز كروماتوگرافي متصل به طيف‌سنج جرمي (GC/MS) شناسايي شد. سپس فعاليتهاي آنتي‌اكسيداني و راديكال‌زدايي اسانسها مورد سنجش قرار گرفته و تاثير ضد ميكروبي آنها ارزيابي شد. ميكروارگانيسمهاي مورد پژوهش، E. coli، S. aureus، S. enteritidis و L. monocytogenes بودند. نماي حساسيتي ميكروارگانيسمها و حداقل غلظت مهاركنندگي و كشندگي (MIC, MBC) روغنهاي اسانسي تعيين گرديد. سينتيك مرگ ميكروبي نيز بر اساس مدت زمان تاثير كشندگي اسانسها مورد بررسي قرار گرفت. خواص آنتي‌اكسيداني روغنهاي اسانسي تعيين و رابطه آنها با خواص ضد ميكروبي اسانسها بررسي گرديد. در اسانسهاي Mentha spicata و Chenopodium ambrosioides به‌ترتيب 14 و 13 تركيب شناسايي شد. L. monocytogenes، E. coli، S. aureus و S. enteritidis به‌ترتيب نسبت به اسانسها حساسيت نشان دادند. تاثير ضد ميكروبي برگ پونه قويتر از سلمك معطر بود. ارزش D باكتريهاي E. coli، S. aureus، S. enteritidis و L. monocytogenes در برابر اسانسهاي پونه و سلمك معطر به‌ترتيب (28/4 و 5)، (8/2 و 5)، (42/6 و 42/6) و (5 و 28/4) بود. اندازه قطر هاله عدم رشد ارتباط چنداني با سينتيك ميكرب‌كشي آن نداشت. اسانسهاي تحت مطالعه داراي خاصيت آنتي‌اكسيداني مساوي يا برتر در مقايسه با آنتي‌اكسيدان شيميايي BHA هستند. ارتباط مستقيم بين خاصيت آنتي‌اكسيداني با قدرت ضد ميكروبي آنها مورد بررسي قرار گرفت.

Lipid peroxidation is the most important deteriorative effect of free radicals that leads to destruction of cell membrane. The routine use of antioxidants is becoming more limited due to their instability and their probable carcinogenic effects. The use of natural additives and antioxidants in treatment of microbial and non microbial diseases is gaining momentum among people. In the present work, we extract and identify the chemical compounds of the essential oils of Mentha spicata L. and Chenopodium ambrosioides.L. Antioxidative property, free radical scavenging capacity and antimicrobial characteristics of oils were then studied. The microorganisms employed in this study were: E.coli, S.aureus, S.enteritidis, L. monocytogenes. The plants were hydrodistilled and the essential oils were extracted. The chemical constituents of the oils thus obtained were identified by GC/MS. Employing disc diffusion and tube dilution methods antimicrobial effects of the oils on were studied. Zones of microbial growth inhibition and Minimum Inhibitory and Bactericidal concentrations (MIC & MBC) of the microorganisms exposed to various dilutions of the oils were determined. Kinetics of microbial death were determined. Antioxidant properties of the oils were tested and their relation to antimicrobial properties of the oils were studied. Chemical analysis lead to identification of 14 and 13 compounds in the essential oils of Mentha spicata and Chenopodium ambrosioides, respectively. The sensitivity of bacteria to the oils were the order of L. monocytogenes > E. coli > S. aureus > S. enteritidis. The antibacterial properties of the essential oils from Mentha spicata leaves were higher than the oils from C. ambrosioides leaves. The D values for E. coli, S. aureus, S. enteritidis and L. monocytogenes exposed to the MBC levels of the essential oils were: Mentha spicata (6.42, 10, 6.42, 6.42) and Chenopodium ambrosioides (2.85, 4.28, 5, 4.28) minutes respectively. The zones of microbial growth inhibitions were not correlated to microbicidal kinetics of the oils. The oils had antioxidant properties equivalent to or higher than synthetic BHA antioxidant. The correlation between antioxidative properties and antimicrobial activities of the oils were studied.