Leucas zeylanica belongs to Leucas genus (Lamiaceae), which distributes in Baoting, Lingshui, Ledong, Dongfang, Changjiang and Lingao in Hainan Island, China. It has been used as a folk medicine in China, for example, a poultice from its leaves may be taken as a sedative, and heal wounds and sores, itches, headaches and vertigo. L. zeylanica has antioxidant, antibacterial, anthelmintic, and anti-fungal activities. Previous phytochemical investigations on this genus plants have afforded various types of compounds, such as flavonoids, terpenoids, lignans, coumarins, steroids glycosides and fatty acids. Many of them exhibit positive bioactivities. In our ongoing investigation of structural diversity and bio-active natural products from the medicinal plant resources in Hainan Island, research on the chemical constituents of L. zeylanica was explored. This study provides theoretical evidence and material basis for further development and utilization of L. zeylanica.
　　Forty-two compounds, including a new one, were isolated from the plant through column chromatography over Silica gel, Sephadex LH-20, and semi-preparative HPLC. Their structures were elucidated on the basis of spectroscopic methods, including HR-EI-MS, ESI-MS, 1D and 2D NMR. The structural types of the isolates including norditerpenoids, flavonoids, flavonoid glycosides, lignans, terpenoids, steroids, alkaloids and benzene derivatives, etc.
　　Someoftheisolatedcompoundswereevaluatedfortheirinhibitoryactivitiesofα-glucosidaseinhibitoryandABTSradicalscavengingactivities.Compounds5-(hydroxymethyl)-4,7-dimethoxy-2H-chromen-2-one(42),catechol(21),isolariciresinol(33),andethylcaffate(16)showedsignificantinhibitoryactivitiesonα-glucosidasewithIC50valuesof0.57,1.69,2.8,and3.51mM,respectively(positiveacarboseIC50=4.7±0.12mM).Compounds33,buddlenolE(30),darendosideB(31),andethylcaffate(16)displayedpotentialABTSradicalscavengingactivitieswithIC50valuesof0.17,0.26,0.33and0.46mM,respectively(positivecontroltroloxIC50=0.47±0.01mM).