Cellular localisation and quantification of Camptothecin in different plant parts of Nothapodytes nimmoniana (J. Graham) Mabberley of Sri Lankan origin.

Abstract

Nothapodytes nimmoniana (Icacinaceae) is a rich source of Camptothecin (CPT), an anti-cancer prodrug. Efficient extraction of CPT from various plant parts is crucial for better recovery of this pre-drug. To investigate the distribution of CPT in plant parts and to compare the methods of extraction on CPT yield to evaluate how cellular localisation affects the efficiency of extraction methods. Transverse sections of plant parts were observed under a ultraviolet (UV)-fluorescence microscope for the fluorescence that the CPT molecule emits when exposed to UV radiation. Dried plant parts were extracted using 90% methanol with ultrasonic assistance, hot ethanol (61% ethanol at 60°C), and chloroform-methanol (4:1, v/v). The CPT in plant parts were detected by thin-layer chromatography (TLC) and confirmed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and high-performance liquid chromatography (HPLC). Quantification was carried out by HPLC. Blue fluorescence indicated a prominent accumulation of CPT in roots compared to leaf with petiole, twigs, and stembark. This accumulation was observed in upper and lower epidermis of the leaf, isolated strands of fibres in the phloem in the petiole, and groups of idioblast cells in the cortex. The ultrasonic-assisted extraction with 90% methanol showed the highest CPT yield in the root (1.91 ± 0.02 mg/g of dry weight), followed by stembark and the least in leaves [0.02 ± 0.01 mg/g (dry weight)] irrespective of the method of extraction. However, hot ethanol extraction gave the highest CPT yield for twig and leaf, indicating the necessity of tissue-specific extraction methods for better recovery of CPT.