Chemical Constituents And Bioactivities Of Rhodomyrtus Tomentosa (Ait.) Hassk

Rhodomyrtus tomentosa (Ait.) Hassk., an evergreen shrub also known as downy rose myrtle, widely distributing in east to southern China, belongs to the family Myrtaceae. It is a traditional Chinese mecicinal plant under the name of ’Tao-Jing-Niang’. The fruit has long been used in folk medicine to boost the immune system and serves as a tonic after childbirth and a potent antioxidant for health-promoting purposes. The leaf of this plant has been employed to treat colic diarrhoea, dysentery, abscesses, haemorrhage, and gynecopathy.Detailed phytochemical investigation of the leaves of R. tomentosa by various chromatographic methods led to the isolation of18compounds. Spectroscopic analyses (ESI-MS,1H-NMR,13C-NMR, DEPT, HMBC) were employed to determine the structures as lupeol (1), myricetin-3-O-α-L-rhamnoside (2),4,8,9,10-tetrahydroxy-2,3,7-trimethoxyanthracene-6-O-β-D-glucopyranoside (3),2,4,7,8,9,10-tetrahydroxy-3-methoxyanthracene-6-O-α-L-rhamnopyranoside (4), rhodomyrtone (5), kaempferol-3-O-β-L-furanoarabinoside (6),2a,3β,19α,23-tetrahydroxyurs-12-en-28-oic acid β-D-glucopyranosyl ester (7),23-hydroxy tormentic acid (8), laricitrin (9), betulinic acid (10), oleanolic acid (11), stigmasterol (12), myricetin (13), β-sitosterol (14), daucosterol (15), gallic acid (16), methyl gallate (17), and ethyl gallate (18). Compounds6-9,12and13were isolated from this plant for the first time. The in vitro antibacterial and cytotoxic activity of some selected compounds were also evaluated. As a result, compound5displayed potent inhibitory activity against Staphyloccocus aureus, Bacillus subtilis, Bacillus cereus and Salmonella typhimurium with MIC values at0.78μg/mL. It showed equal antibacterial activity with the positive control (Vancomycin). The cytotoxic activity of5against CNE, A549and MCF-7cell lines was also significant with IC50of0.65μg/mL,0.72μg/mL and0.64μg/mL, respectively. And it showed equal cytotoxic activitiy with Doxorubicn (positive control).Since R. tomentosa is recognized an invasive plant, the allelopathic effects of the aqueous extracts from different plant tissues on the seed germination of Arabidopsis thaliana were studied using the indoor petri dish method. The result showed that the allelopathic effects of aqueous extracts from leaf, stem and root on the seed germination varied largely, and the intensity of allelopathic effect of different organs was in the order of leaf> stem> root.The results of this study improve the knowledge on the chemical profile, the key substances responsible for the biological activities, as well as the allelopathic effects of R. tomentosa, which provided a scientific basis for better understanding of its medical and agricultural potentials and integrated utilization.