The rhizome of Kaempferia parviflora or kra-chai-dum (in Thai) is used traditionally as a folk medicine. The preliminary cholinesterase inhibitory screening of this plant extract exhibited significant acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities. Thirteen known methoxyflavones (1-13) were isolated and their structures were completely elucidated based on NMR analysis and compared with literature reports. Minor compounds 12-13 were reported for the first time from this species. The cholinesterase inhibitory test results showed that the highest potential inhibitors toward AChE and BChE were 5,7,4'-trimethoxyflavone (6) and 5,7-dimethoxyflavone (7), respectively, with the percentage inhibitory activity varying over 43-85%. The structure-activity relationship study led to the conclusion that compounds bearing 5,7-dimethoxy groups and a free substituent at C-3 had a significant inhibitory effect at a concentration of 0.1 mg/mL, but those bearing a 5-hydroxyl group reduced the inhibitory potency. On the other hand, flavones bearing a 3'- or 5'-methoxy group did not influence the inhibitory effect. Interestingly, 5,7-dimethoxyflavone (7) exhibited strong selectivity for BChE over AChE which may be of great interest to modify as a treatment agent for Alzheimer's disease.
Cholinesterase (ChE) inhibitory activities of three coumarins (mansorins A-C) and five naphthoquinones (mansonone C, E, G and H) were evaluated to determine the relationships between the acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory effects and the core structures of these compounds. Among the tested compounds, mansonone E exhibited the highest ChE inhibitory activities, with IC₅₀ values in the low micromolar levels. In addition to revealing the ChE inhibitory activities of naphthoquinones for the first time, the results also revealed structure-activity relationship information that could be useful for further modification. Furthermore, the study also supports the hypothesis that mansonones are the active component in Thespesia populnea, a plant that previously has been shown to enhance memory activity in an in vivo study.
Five flavonoids, one isoflavone and five xanthones were isolated from Anaxagorea luzonensis. Of these eleven isolated compounds, 1,3,5-trihydroxy-4prenylxanthone (3) was a relatively potent inhibitor of phosphodiesterase type 5 (PDE5), with an IC 50 value of 3.0 µM. This is the first report showing that natural xanthones can exhibit promising PDE5 inhibitory activity. Moreover, this study revealed that the presence of the C-4 prenyl residue attached to the xanthone core is correlated with the significant PDE5 inhibitory activity.
Summary
A dissolvable and edible carboxymethylcellulose–alginate film with 34% (w/w) of kaffir lime oil (KLO) was prepared. The prepared films can be redissolved in warm water providing highly dispersed KLO microdroplets. The freshly prepared KLO films (KLO film‐0) and 6‐month stored KLO films (KLO film‐6) were evaluated for consumer acceptance in a Thai Tom‐yum soup recipe in comparison with fresh kaffir lime (KL) leaves and commercialised instant Tom‐Yum paste. The data analysis from 120 consumers presented the higher liking scores of the soups using the KLO film‐0 and KLO film‐6 on aroma, taste and overall preference than those using the instant Tom‐Yum paste and the KL leaves. Additionally, chefs noted a longer lasting aroma intensity of the soups prepared with KLO films. Thus, this edible KLO film can be used in place of fresh KL leaves with the additional benefits of a long shelf‐life, ease of use and better consumer preferences in Tom‐Yum soup cooking.
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