Seasonal and genotypic variation of water-soluble polysaccharide content in leaves of Cyclocarya paliurus

Cyclocarya paliurus (Batal) Iljinskaja is an important medicinal woody plant due to numerous bioactive natural products in its leaves. As an important bioactive natural product, water-soluble polysaccharides (WSP) in leaves of C. paliurus possess diverse biological activities, such as hypoglycemic, anticancer and free-radical-scavenging activities. To better understand accumulation patterns of WSP in C. paliurus leaves, seasonal, genotypic and positional variations of WSP content were investigated in this study. The results showed that the mean content of WSP in leaves from three crown positions (upper, middle and lower) within an individual was 38.5 mg g ⁻¹. ANOVA and Duncan's multiple range test indicated that WSP content in leaves of the upper crown was significantly higher than that in the middle and lower crowns, whereas no significant difference was observed between the middle and the lower positions. Seasonal variation of WSP content in the leaves was revealed as a bimodal temporal pattern with the maximum (38.3 mg g ⁻¹) observed in April and the second peak (32.3 mg g ⁻¹) in October, whereas the lowest WSP content was observed in June (20.12 mg g ⁻¹) or in fallen leaves (17.71 mg g ⁻¹). Generally, higher contents of WSP accumulated in the maturity/senescence period (from September to mid-November) than during the rapid growth phase (from May to August). Moreover, WSP content varied significantly among 12 provenances, ranging from 22.09 to 34.56 mg g ⁻¹, in leaves sampled in October. Our results not only provide knowledge of the accumulative dynamics and genotypic variation of WSP, but also establish a basis for determining the optimal time for harvesting and for extensive selection and breeding programs to improve the content of beneficial compounds in the leaves of C. paliurus in the future.