Abstract
Blueberries have seen an ascending production line boosted by World Health Organization (WHO) approvals for their contributions to a healthy diet and the evidence that they act against different diseases. This increase resulted in significant amounts of discarded leaves, which could be a valuable source of bioactive compounds. In the present study, ultrasound-assisted extraction technology was used to determine and compare the chemical and biological profiles of leaves from six commercial blueberry (Vaccinium corymbosum L.) varieties. Feruloylquinic acid was the major compound identified, ranging from 19.23 ± 0.18 mg/g (at the lowest level, registered in the Spartan variety) to 49.62 ± 0.41 mg/g (at the highest level, registered in the Nelson variety). Rutin was the second major compound identified, for which Toro, Nelson, and Elliot leaves registered the highest values, with 35.77 ± 0.19 mg/g, 32.50 ± 0.20 mg/g, and 31.53 ± 0.1 mg/g, respectively. Even though analogous polyphenols were detected in the six cultivars, their concentrations and amounts were different. The leaf extracts of the cultivars Toro, Elliot, and Nelson appear to be good sources of antioxidants, registering high percentage inhibitions of DPPH radicals, of 70.41%, 68.42%, and 58.69%, respectively. The blueberry leaf extracts had a strong antibacterial activity and a low antifungal capacity, and a low-to-moderate antimutagenic capacity towards Salmonella typhimurium TA98 and TA100 strains, with Toro leaf being the best candidate. All of these biological activities indicate health-related benefits, recommending them as suitable candidates for medical and pharmaceutical applications. The present paper adds significant knowledge to the field of blueberry leaves via chemical and biological profiles, supporting the ultrasound-assisted extraction technique as a useful and green method to provide alternative sources of bioactive compounds.
Highlights
Current evidence has underlined the fact that the overproduction of reactive oxygen species (ROS)and free radicals may be responsible for several pathological reactions that could contribute to the occurrence of specific diseases such as cancer, atherosclerosis, diabetes, and rheumatoid arthritis [1,2,3].Plants 2020, 9, 1193; doi:10.3390/plants9091193 www.mdpi.com/journal/plantsmore bacteria have become resistant to well-established antibiotics, underlying the emergent need for novel/natural anti-microbial molecules [4,5,6,7,8]
In the leaves of the six Romanian blueberry cultivars were identified 19 phenolic compounds belonging to four phenolic classes: hydroxycinnamic acids, flavonols, flavanols, and anthocyanins (Table 1)
The best-represented subclasses in terms of the number of phenolic compounds were flavanols and flavonols, while the most abundant group in terms of the highest levels, for all six varieties, were hydroxycinnamic acids
Summary
Current evidence has underlined the fact that the overproduction of reactive oxygen species (ROS)and free radicals may be responsible for several pathological reactions that could contribute to the occurrence of specific diseases such as cancer, atherosclerosis, diabetes, and rheumatoid arthritis [1,2,3].Plants 2020, 9, 1193; doi:10.3390/plants9091193 www.mdpi.com/journal/plantsmore bacteria have become resistant to well-established antibiotics, underlying the emergent need for novel/natural anti-microbial molecules [4,5,6,7,8]. The plant kingdom is a rich complex of bioactive compounds [9,10,11,12,13]. In this context, plant-based antioxidant compounds have received increased attention due to their ability to protect the human body against free radicals without—or with fewer—side effects [14,15]. The Vaccinium corymbosum (V. corymbosum) plant, known as blueberry, has been reported as a complex of antioxidant and antimicrobial molecules—more precisely, polyphenol compounds—with a wide range of anthocyanins [18,19,20,21]. The Blueberry, Vaccinium spp., is a perennial shrub which is well-known worldwide, whereas the northern highbush blueberry (V. corymbosum L.) is the most popular [22,23,24]
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