Seasonal effect of plumbagin concentration in plumbago zylenica L roots during floral development of the Ugandan medicinal herb

Plumbago zylenica L is a common Ugandan herb rich in phytochemical compound plumbagin used in the management of many ailments including malaria fevers. Following the general WHO herbal good agricultural and collection practices guidelines, it is demanded that each Nation publish country specific guidelines for sustainable availability of quality raw materials and standardized ingredients of important medicinal plants. Consequently, the WHO general guideline which stated that plumbago zylenica roots best be harvested once in six months at 50% flowering, without taking out whole roots is still unclear as it does not point out whether to collect the flowering or the non flowering in the group. Therefore, an urgent need for a more specific and inclusive guideline when Ugandan P. zylenica roots were to be harvested was realized. Previously, the main phytochemicals from P. zylenica (an evergreen herb) were naphthoquinones, flavonoids, terpenoids and steroids. The plumbagin naphthoquinone content was studied during different physiologic developmental stages relative to floration using high performance liquid chromatography. This study was designed to assess the plumbagin concentration in roots of plumbago zylenica L. before and during the floral development in order to analyze the influence of physiological stages and weather in plumbagin production. The well identified botanicals were washed with water, shade dried and pounded using a metallic motar and pestle. The powder was soaked into aqueos ethanol and extraction was by the cold maceration for 3 days. The Buchii type 114 rotary evaporator was used for concentration at 45°C to yield crude extracts for subsequent analyses. Shimadzu high performance liquid chromatography system (Kyoto, Japan), liquid chromatography Solution Version 1.21 was used for the high performance liquid chromatography analyses. The average content of plumbagin in P. zylenica was statistically greater for the samples collected from the just about to flower (before floration) whose value was 0.38±0.015ug/ml as compared to those that were collected during floration (0.35±0.010)ug/ml (P<0.05). Samples of the Ugandan P. zylenica roots yielded significantly more plumbagin when collected from the just about to flower herbs during sunny conditions versus those collected at floration during heavy rainy conditions.