Evaluation of the antimicrobial activities of ultrasonicated spinach leaf extracts using RAPD markers and electron microscopy

Abstract

Spinach (Spinacia oleracea L.) leaves represent an important dietary source of nutrients, antioxidants and antimicrobials. As such, spinach leaves play an important role in health and have been used in the treatment of human diseases since ancient times. Here, the aims were to optimize the extraction methods for recovering antimicrobial substances of spinach leaves, determine the minimum inhibitory concentrations (MICs) of the antimicrobial substances against Escherichia coli and Staphylococcus aureus and, finally, evaluate the effects of spinach leaves' antimicrobials on bacterial DNA using central composite face-centered methods. The effect of the extracts on both Gram-positive and Gram-negative bacterial models was examined by scanning electron microscopy (SEM) and random amplification of polymorphic (bacterial) DNA (RAPD). The optimal extraction conditions were at 45 °C, ultrasound power of 44% and an extraction time of 23 min. The spinach extracts exhibited antimicrobial activities against both bacteria with MICs in the 60-100 mg/ml range. Interestingly, SEM showed that the treated bacterial cells appear damaged with a reduction in cell number. RAPD analysis of genomic DNA showed that the number and sizes of amplicons were decreased by treatments. Based on these results, it was inferred that spinach leaf extracts exert bactericidal activities by both inducing mutations in DNA and causing cell wall disruptions.

Edible Leafy Plants from Mexico as Sources of Antioxidant Compounds, and Their Nutritional, Nutraceutical and Antimicrobial Potential: A Review

“…According to Holetz et al [ 131 ], the extracts of Cestrum nocturnum , Eryngium foetidum , Persea americana , Porophyllum ruderale , Sechium edule , and Solanum torvum are classified as having good antimicrobial activity (MIC less than 100 μg/mL; Table 5 ), while the extracts of Phytolacca americana were moderate (IMC from 100 to 500 μg/mL), and the extracts of Solanum trilobatum , Dysphania ambrosioides and Chenopodium ambrosioides were considered inactive (IMC greater than 1000 μg/mL). Most quelites displayed higher antimicrobial activity than did the most consumed vegetables, as was the case for the following: Lactuca sativa (IMC of 2500 μg/mL) against Escherichia coli (ATCC25922), Klebsiella pneumoniae CI, Staphylococcus aureus and Bacillus subtilis ATCC 6633 [ 132 ]; Spinacia oleracea (IMC of 60,000–70,000 μg/mL) against S. aureus (ATCC 29213) and E. coli OH157:H7 (ATCC 25922) [ 133 ]; and Brassica oleracea (IMC of 2500–20,000 μg/mL) against E. coli O157:H7 ATCC 35150, Salmonella typhimurium ATCC 14028, Listeria monocytogenes ATCC 35152, B. cereus ATCC 11778 and S. aureus [ 134 ].…”

Recombinant Actifensin and Defensin-d2 Induce Critical Changes in the Proteomes of Multidrug-Resistant Pseudomonas aeruginosa and Candida albicans

“…AMPs represent a part of the innate immune system in almost all classes of life ( 8 ) and have been reported to exhibit multiple drug targets simultaneously, making them less prone to resistance ( 9 ). Defensin-d2 is a cationic cysteine-rich plant defensin that was isolated from the leaves of Spinacia oleracea (spinach), which is a widely distributed leafy vegetable renowned for its nutritional benefits and antimicrobial activity ( 10 – 12 ). Defensin-d2 has been reported to be active against phytopathogens, including Pseudomonas syringae , Clavibacter michiganensis , Ralstonia solanacearum , and Fusarium culmorum ( 10 – 12 ), but little is known regarding its activity against human pathogens.…”

“…Defensin-d2 is a cationic cysteine-rich plant defensin that was isolated from the leaves of Spinacia oleracea (spinach), which is a widely distributed leafy vegetable renowned for its nutritional benefits and antimicrobial activity ( 10 – 12 ). Defensin-d2 has been reported to be active against phytopathogens, including Pseudomonas syringae , Clavibacter michiganensis , Ralstonia solanacearum , and Fusarium culmorum ( 10 – 12 ), but little is known regarding its activity against human pathogens. Further, actifensin is a novel bacteriocin produced by Actinomyces ruminicola , which, like plant defensins, is cysteine-rich and contains disulfide bonds ( 13 ).…”

Antibacterial and Antifungal Activity of Plant Extracts from Spinacia oleraceae L. (Amaranthaceae)

“…This is a good source of vitamin K (8) which helps in blood clotting. Spinach is beneficial source for various carotenoids and lipophilic active compounds and decreasing the risk of many diseases such as heart disease, diabetes, neurodegenerative disease and obesity [17,[22][23][24][25][26]. The present study was conducted to evaluate antimicrobial effects of ethanolic extracts of Spinach oleracea root, stem and leaves against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Salmonella enteric isolates.…”