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Fulltext Effect of drying methods on yield, physicochemical properties, and total polyphenol content of chamomile extract powder

Lee SY, Ferdinand V, Siow LF

Front Pharmacol, 2022;13:1003209.
PMID: 36408266 DOI: 10.3389/fphar.2022.1003209

Chamomile (Matricaria chamomilla L.) is a traditional medicinal plant used to treat hay fever, inflammation, muscle spasms, menstrual disorders, insomnia ulcers, wounds, gastrointestinal disorders, rheumatic pain, and hemorrhoids. Dried chamomile flowers have a longer shelf life and the dried extract in form of powder offers much flexibility for new therapeutic formulations as it could be used as a replacement for liquid extract and serve as a shelf-stable ingredient in new applications. This study aims to determine the effect of drying methods, i.e., convection oven-drying at 45 °C, freeze-drying at -50°C, and spray-drying at 140°C at 10.5 and 12 ml/min, respectively) on powder yield, physicochemical properties (moisture content, water activity, and color attributes), and total polyphenol content of chamomile extract powder. Our findings showed that spray-drying conducted at 140°C, 12 ml/min resulted in the lowest yield of powder (16.67%) compared to convection oven-drying (90.17%) and freeze-drying (83.24%). Decreasing the feed flow rate to 10.5 ml/min during spraying caused an increase in powder yield to 26.99%. The moisture content of spray-dried chamomile extract powder obtained at 140°C, 10.5 ml/min was higher (11.00%) compared to that of convection oven-dried (8.50%) and freeze-dried (7.50%). Both convection oven-dried and freeze-dried chamomile extract powder displayed no significant difference (p > 0.05) in moisture content. The higher feed flow rate (12 ml/min) in spray-drying also led to an increase in the moisture content of chamomile extract powder to 12.00%. The higher residual moisture found in the spray-dried samples resulted in partial agglomeration of particles. In terms of water activity, freeze-dried chamomile extract powder was found to have the highest water activity (0.63) compared to that of convection oven-dried (0.52), spray-dried at 140°C, 10.5 ml/min (0.57), and spray-dried at 140°C, 12 ml/min (0.58). Spray-dried and freeze-dried chamomile extract powder with high moisture content and water activity could be highly susceptible to microbial growth. In terms of color attributes, higher drying temperature in spray-drying led to darker, redder, and more yellowish chamomile extract powder that could be caused by heat-induced Maillard reaction and caramelization. Since lower drying temperature was used in both convection oven-drying and freeze-drying, both convection oven-dried (56.94 mg GAE/g powder) and freeze-dried chamomile extract powder (55.98 mg GAE/g powder) were found to have higher total polyphenol content compared to those of spray-dried (42.79-46.79 mg GAE/g powder). The present findings allow us to understand the effect of drying methods on the properties of chamomile extract powder and provide a better drying option to dry chamomile extract. Due to higher powder yield with ideal powder properties such as low moisture content and water activity, desirable color, and high total polyphenol content obtained from convection oven-drying, convection oven-drying was a better option than freeze-drying and spray-drying for drying chamomile extract.
Fulltext The seasonal dynamics and biting behavior of potential Anopheles vectors of Plasmodium knowlesi in Palawan, Philippines

Malijan RPB, Mechan F, Braganza JC, Valle KMR, Salazar FV, Torno MM, et al.

Parasit Vectors, 2021 Jul 07;14(1):357.
PMID: 34233742 DOI: 10.1186/s13071-021-04853-9

BACKGROUND: A small number of human cases of the zoonotic malaria Plasmodium knowlesi have been reported in Palawan Island, the Philippines. Identification of potential vector species and their bionomics is crucial for understanding human exposure risk in this setting. Here, we combined longitudinal surveillance with a trap-evaluation study to address knowledge gaps about the ecology and potential for zoonotic spillover of this macaque malaria in Palawan Island.
METHODS: The abundance, diversity and biting behavior of human-biting Anopheles mosquitoes were assessed through monthly outdoor human landing catches (HLC) in three ecotypes representing different land use (forest edge, forest and agricultural area) across 8 months. Additionally, the host preference and biting activity of potential Anopheles vectors were assessed through comparison of their abundance and capture time in traps baited with humans (HLC, human-baited electrocuting net-HEN) or macaques (monkey-baited trap-MBT, monkey-baited electrocuting net-MEN). All female Anopheles mosquitoes were tested for the presence of Plasmodium parasites by PCR.
RESULTS: Previously incriminated vectors Anopheles balabacensis and An. flavirostris accounted for > 95% of anophelines caught in longitudinal surveillance. However, human biting densities were relatively low (An. balabacensis: 0.34-1.20 per night, An. flavirostris: 0-2 bites per night). Biting densities of An. balabacensis were highest in the forest edge, while An. flavirostris was most abundant in the agricultural area. The abundance of An. balabacensis and An. flavirostris was significantly higher in HLC than in MBT. None of the 357 female Anopheles mosquitoes tested for Plasmodium infection were positive.
CONCLUSIONS: The relatively low density and lack of malaria infection in Anopheles mosquitoes sampled here indicates that exposure to P. knowlesi in this setting is considerably lower than in neighboring countries (i.e. Malaysia), where it is now the primary cause of malaria in humans. Although anophelines had lower abundance in MBTs than in HLCs, An. balabacensis and An. flavirostris were caught by both methods, suggesting they could act as bridge vectors between humans and macaques. These species bite primarily outdoors during the early evening, confirming that insecticide-treated nets are unlikely to provide protection against P. knowlesi vectors.

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