Response Of The Secondary Metabolites In Camptotheca Acuminata Seedlings To Light Intensity

Camptotheca acuminata Descne is a native tree of China. Camptothecin (CPT), a monoterpene indole alkaloid in C. acuminata, has high anticancer activities. It was determined by HPLC that the secondary metabolites in roots, stems and leaves of Camptotheca acuminata seedlings under different light intensities in the greenhouse. The seasonal changes of the secondary metabolites in different organs, their response to light intensity, the relativities between CPT and other secondary metabolites were investigated, respectively. The main results are as follows:(1) A method for the determination of the secondary metabolites in Camptotheca acuminata by HPLC was established. Samples were ultrasonically extracted by methanol for 30 min. The secondary metabolites were separated on a U.K. Hypersil GOLD C18 column (250 mm×4.6 mm , 5μm) , using methanol-aqueous solution (2 mL acetic acid in 100 mL H₂O) as the mobile phase at flow rate 1.0 mL/min. The detective wavelengthes were 210-400 nm by diode-array detection. The gradient program included four linear steps, the ratio of methanol was increased from 5% to 30% in first 30 min, and then at 70 min, 80min, and 85 min raised to 50%, 80% and 100% respectively.24 compounds (numbered from 1 to 24, CPT was No. 16) were separated from seeds, roots, stems and leaves of Camptotheca acuminata, and there were differences among different organs.(2) The changes of the secondary metabolites in roots at different growth stages were more than those in leaves. The changes in stems were least. Except compound 20, the other secondary metabolites all trended to decrease with the growth of Camptotheca acuminate seedlings. Compound 20 in roots began increasing obviously from Aug. 27. In the 75 days from Jul. 13 to Sep. 26, the maximum difference of the secondary metabolites in roots was between Jul. 28 and Aug. 27. The change of the secondary metabolites in stems between Jul. 28 and Sep. 26 was most obvious. For the secondary metabolites in leaves, the differences of between Aug. 12 or Aug. 27 and Sep. 26 were both more than others.With the seedling growth, the allocation ratio of the secondary metabolites in different organs changed. But the maximum allocations of CPT and compound 2, 3, 7, 8, 11, 15, 17 were all in leaves. The ratio of compound 10 in roots was highest, followed by that in leaves. On Jul. 28 the maximum allocation of compound 24 was in leaves, but from Aug. 12 to Sep. 26 that was in roots.(3) The responses of the secondary metabolites in leaves of Camptotheca acuminate seedlings to different light intensity were the most obvious. Those in roots were second to them.Those in stems were least. Compared with those in full sunlight, the changes of the secondary metabolites in roots after 15, 45, 60 and 75 days of treatment in 30% of full sunlight were more obvious. When the irradiance decreased to 60% of full sunlight, the effect of light intensity on the secondary metabolites in roots was more after 30 days of treatment. The difference of the secondary metabolites in stems between in 60% of full sunlight and in full sunlight was larger after 15 days of treatment, but after 30 days of treatment that between in 30% of full sunlight and in full sunlight was more obvious. From the 45th day to the end of shading treatment, light intensity hardly influenced the secondary metabolites in stems. Longer shading treatment (60 days or 75 days) affected the secondary metabolites in roots and leaves more.When the irradiance decreased to 60% of full sunlight, the contents of CPT in leaves of Camptotheca acuminate seedlings after 15 days and 75 days of treatment were more 20% and 80% than those in full sunlight, respectively. In 60% of full sunlight the content of CPT in stems after 60 days of treatment was also higher than that in full sunlight. When the irradiance decreased to 30% of full sunlight, the accumulations of CPT in leaves and stems were worse, but the content of CPT in roots after 45 days of treatment was 2 times than that in full sunlight. Light intensity also affected the accumulation of other secondary metabolites in different organs, but there were no rules.The allocations of the secondary metabolites in Camptotheca acuminate seedlings to organs were influenced by light intensity, and no rules existed, too.(4) In roots of Camptotheca acuminate seedlings, the regression coefficients between CPT and compound 19 or 24 were higher than others. Those between CPT and compound 2 or 10 in stems were the best. The regression relations between CPT and most secondary metabolites in leaves were the power. Thereinto, the regression coefficient of compound 3 was highest.