RESUMEN
Blumea balsamifera (L.) DC., belonging to the Asteraceae family, also known as "ngai camphor," is one of the traditional herbs used in Thailand for folk medicine and a component in local food and drinks. There was, however, no evidence indicating the presence of beneficial compounds at different leaf ages. Exploring various extraction solvents, we investigated the phenolics, flavonoids in particular quercetin content, antioxidant capacity, and antibacterial activity of immature and mature leaf extracts. The dried leaves were macerated in 50% ethanol, 95% ethanol, hexane, or decocted in water. Bioactive substances were analyzed by UV spectrophotometry and HPLC. Analysis of antioxidant capacity was done byDPPH, ABTS, FRAP, and NO scavenging assays. The antibacterial activity of immature leaf extract eluted with 50% ethanol was subsequentially evaluated in vitro. Extraction with 50% ethanol proved optimal, yielding 1.2-1.6-fold and 1.5-fold greater immature and mature leaf extracts than other solvents. More phenolics (1.2-fold), flavonoids (1.1-fold), quercetin content (4.8-fold), and antioxidant activity (1.3-fold) were found in the immature leaf extract. There was a significant positive correlation between antioxidant activity and bioactive compounds. The immature leaf extract eluted with 50% ethanol showed antibacterial activity against Staphylococcus aureus, with a minimum inhibitory concentration of 0.5 mg/mL. The immature leaves of B. balsamifera are a rich source of quercetin and phenolics, and 50% ethanol proved optimal for extracting bioactive components from these leaves.
RESUMEN
The fates of seeded Escherichia coli O157:H7 and Salmonella on selected fresh culinary herbs were evaluated at a refrigerated temperature (4 degrees C). Fresh herbs, including cilantro, oregano, basil, chive, parsley, and rosemary, were inoculated with six-strain mixtures of E. coli O157:H7 and Salmonella, and the microbial populations were monitored at 1, 5, 11, 16, 19, and 24 days. For both pathogens, a significant decrease in the population (P < 0.0001) occurred within the first 5 days of storage (< 0.8 log). Both pathogens remained the highest on cilantro and the lowest on rosemary (P < 0.0001). Storage time had a significant effect on the survival of E. coli O157:H7; populations declined as storage time progressed. Although storage of cilantro, basil, and chive was terminated after 19 days because of deteriorated quality, significant numbers of both pathogens were recovered from the remaining fresh herbs after 24 days of storage. The results showed that both bacteria were extremely persistent on all test herbs under the test conditions. The results also reinforce the concept that, once contaminated, bacterial pathogens can persist on fresh herbs throughout a normal distribution time.