Abstract
Muriolide (MO) is a natural lactone that was isolated from Ranunculus muricatus. This compound exhibited good antioxidant activity in some experiments; however, the radical scavenging activity of MO in physiological environments has not been studied yet. In this study, the reaction between hydroperoxyl radical and MO was investigated in physiological environments by using density functional theory (DFT) calculations. It was found that MO exhibits excellent antiradical activity in water at physiological pH (k = 1.05 × 108 M−1 s−1) by the single electron transfer mechanism of the anion state. However, the activity in lipid media is moderate with k = 2.54 × 104 M−1 s−1 and is defined by the formal hydrogen transfer pathway. The antiradical reactions can occur in double processes; however, the first reaction may define the HOO˙ radical scavenging activity of MO. Compared with typical natural antioxidants, the antiradical activity of MO against HOO˙ radicals is slightly lower than Trolox in pentyl ethanoate. However, the activity of MO is approximately 808 times faster than that of the reference in aqueous solution. Thus, the data suggest that MO is a promising natural radical scavenger in the physiological environment.
Highlights
Ranunculus muricatus, which belongs to the genus Ranunculus (Ranunculaceae), is known as spiny fruit buttercup in Asia, Australia, South America, and Europe.[1]
The antioxidant activity of R. muricatus may be related to phenolic compounds such as avonoids, avonoid glycosides, and lactones found in the plant.[7,9,10]
The hydroperoxyl radical scavenging activity of muriolide in the physiological environment has been successfully investigated in silico
Summary
Ranunculus muricatus, which belongs to the genus Ranunculus (Ranunculaceae), is known as spiny fruit buttercup in Asia, Australia, South America, and Europe.[1] The plant has been used as a traditional drug to treat urinary infections, jaundice, diarrhea, dysentery, eczema, leprosy, and ringworm infection.[2,3,4] R. muricatus is used as a remedy for coughs and asthma and a deworming agent for all types of livestock.[5,6] Studies showed that R. muricatus exhibited cytotoxic, antibacterial, antifungal, and antioxidant properties.[7,8] The antioxidant activity of R. muricatus may be related to phenolic compounds such as avonoids, avonoid glycosides, and lactones found in the plant.[7,9,10]. Muriolide (MO, Fig. 1) is a natural lactone that has been isolated from Ranunculus muricatus.[9] This compound exhibited good antioxidant activity against the DPPH radical scavenging activity (IC50 1⁄4 56.9 mM) and lipoxygenase enzyme testing (IC50 1⁄4 68.3 mM). The radical scavenging activity of MO, in the physiological systems, needs to be investigated; this issue has not been mentioned yet. The effects of solvents and molecule structure on the activity were considered
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