| Nuclear radiation is widely used in the filed of military, energy, health, agriculture etc, however, it is also of tromendous concern in terms of public security. Developing safe and effective radiation protectant is of great importance. The bamboo leaves, with diversed secondary metabolites, have been shown to have significant biological effects such as free radical scavenging activity, anti-radiation, anti-aging, anti-bacterial, anti-viral, enhancing immunity and others. Recent studies showed that at concentration of20～160μg/mL, bamboo leaf flavone [butanol fraction from70%ethanol extract of Phyllostachys nigra var. hnonis (Bean) Stepf ex Rendle] could prevent DNA from60Co-y irradiation damage. However, this radioprotection effects have not been confirmed by in vivo studies. Till now, the utilization of bamboo leaves focus mainly on family Phyllostachys, which has tall stem and small leaves and is difficult to harvest. The present study is designed to analyze the radioprotection effects of several bamboos grasses, namely Shibataea chinensis Nakai, Pleioblastus kongosanensis f. aureostriatus Muroi et Yuk Tanaka, Indocalamus latifolius (Keng) McClure, Sasa pygmaea (Miq.) E. G. Camus, Sasa argenteastriatus E.G. Camus and Sasa veitchii (Carr.) Rehd. These bamboo grasses have abundant active compounds and high antioxidant activity, meanwhile, they have rapid growth rate, lush foliage and are easy to harvest. Therefore, they have the potential to be developed as a kind of leafy bamboo grove. Firstly, the content of active components, antioxidant activities and DNA damage prevention abiligy of the above six bamboo grasses leaf were investigated. Then, the most reprensative and potential P. kongosanensis f. aureostriatus was selected. Its effective parts of the selected bamboo grass were screened by detecting the active components content and relalated chemical compounds. And finally, the study of radioprotection ability of the effective parts was carried out and its protective functions were also determined. The main conclusions are as follows:(1) The content of active components, antioxidant activities and DNA damage prevention ability of the above six bamboo grasses leaves were compared. S. chinensis and P. kongosanensis f. aureostriatus contains higher total phenolic (9.12% and5.51%, respectively), total flavonoids (4.00%and3.16%, respectively) and titerpenoids (2.28%and1.89%, respectively) content than the others. The antioxidant activity and DNA damage prevention ability of those two species were also stronger than others (p<0.05). Taking into account factors such as leaf size, collection and cultivation, P. kongosanensis f. aureostriatus with the advantage of larger leaf, easier picking and wider range of cultivation, was selected as the further research object.(2) The biomass of P. kongosanensis f. aureostriaus was observed. Results show that the leaf biomass of P. kongosanensis f. aureostriaus was746.53g/m2, which is of2.13times of that of Phyllostachys pubescens Mazel ex H. de Lehaie (350.5g/m2). It means P. kongosanensis f. aureostriaus have the advantage to be developed as a kind of leafy bamboo grove.(3) Changes of the antioxidant activity and active compounds content from P. kongosanensis f. aureostriatus affected by different harvest season and pre-treatment were investigated. Results showed that bamboo grasses leaf have the highest level of total active components and antioxidant activity in autumn-winter. Different drying methods also affected the active compounds. The bamboo leaf which is collected from September and treated by hot air drying contained significant higher total phenolic (3.15%), total flavonoids (1.98%), titerpenoids (2.28%) and stronger DPPH radical scavenging ability (IC50502.00μg/mL, DW) than other drying methods, i.e. shade drying, sunny drying and microwave drying (p<0.05). The DPPH radical scavenging IC50reached404.32μg/mL by using an extraction temperature70℃, material/liquid ratio1:25, extraction duration80min and the ethanol concentration70%. Additionally, UV treatment of low dosage (1kJ/m2) which can effectively enhance the content of total phenolic56.66%, total flavonoids41.94%, DPPH radical scavenging ability10.30%, is a convenient, economical and effective pre-treatment method for bamboo leaf.(4) The effective part of P. kongosanensis f. aureostriatus leaf extract was selected by active components content and biological activity determination. The70%ethanol extract of P. kongosanensis f. aureostriatus (PLE) and its four different polarity fractions i.e. petroleum ether fraction (PLE-PF), ethyl acetate fraction (PLE-EF),n-butanol fraction (PLE-BF) and water fraction (PLE-WF) showed concentration dependent scavenging ability on DPP·、ABTS·+、·OH、O·2-、H2O2and DNA damage prevention ability. PLE-BF had the highest yield rate (7.49%, DW) and total flavonoids content (18.97%) while PLE-EF possessed the highest content of total phenolic (32.42%) and titerpenoids (7.37%). Both two fractions showed the highest antioxidant activity and DNA damage prevention ability than others (p<0.05). Thus, in practice, PLE-BF and PLE-EF were combined and supposed to be the effective part of P. kongosanensis f. aureostriatus leaf extract (PLE-EP).(5) The characteristic compounds of P. kongosanensis f. aureostriatus leaf were isolated, purified and structural analyzed. By using normal phase and reversed-phase silica gel column, RP-C18, Sephadex LH-20and thin-layer chromatography, five compounds were isolated from PLE-EP. They were identified as p-coumaric acid, ferulic acid, kurilensin A, siparunoside and tricin. The contents of them were measured by RP-HPLC, with a value of11.30,2.05,12.64,3.18and8.79mg/g in PLE-EP. Free radical scavenging effect (DPPH·, ABTS·+), reducing power and DNA damage prevention ability of each compounds were also investigated. Kurilensin A showed significant stronger antioxidant activity and DNA damage prevention ability than others (p<0.05), was referred to be the main active compound in P. kongosanensis f. aureostriatus leaf.(6) The radioprotection ability of P. kongosanensis f. aureostriatus leaf were determined using animal test. In the60Co.y radiation injured mice, both PLE-EP and bamboo leaf flavonoids (BLF-d24) was able to significantly improve the survival of the treated mice in the30d test at the dose of200mg/kg-d. Also, they decreases the white blood cell, red blood cell, platelet counts and hemoglobin level in the peripheral blood of the radiation injured mice. After3weeks administration, the white blood cell counts of radiation injured mice was significantly improved (p<0.05). Additionally, PLE-EP (400mg/kg-d) was able to rescue nucleated cells in treated mice bone marrow to normal level and significantly reduce its micronucleated polychromatic erythrocytes. Futhermore. both PLE-EP and BLF-d24was shown to elevate the endogenous antioxidant enzymes (SOD、GSH-Px、CAT) activities and reduce the MDA、LPO、LF content, and protect the liver, thymus and spleen of mice from irradiation injury to different degrees.In conclusion, P. kongosanensis f. aureostriatus leaf extract showed significant antioxidant activities, DNA damage prevention ability, and effective effect on protecting organism from irradiation injury. Phenolic acid and flavonoids were the main active compounds. P-coumaric acid, ferulic acid, kurilensin A, siparunoside and tricin is the first time detected from P. kongosanensis f. aureostriatus. Furthermore, kurilensin A has never been reported in Phyllostachys bamboo so far, while siparunoside was first time reported in bamboo. Kurilensin A, with strong antioxidant activity and DNA damage prevention ability, was the key active compound in P. kongosanensis f. aureostriatus leaf contributing its antioxidant activity and radioprotection ability. In addition, P. kongosanensis f. aureostriatus with the advantage of fast growing and large leaf biomass have the potential to be developed as a kind of leafy bamboo grove.Results of this study expanded a new space for bamboo chemical elements and modern biological utilization of bamboo resources. |
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