Ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry metabolomic profiling reveals harvest age dependent changes in the roots of Pelargonium sidoides DC.

Abstract

Introduction: Cultivation of medicinal plants provides an opportunity for economic gain and health care accessibility. Ensuring consistent quality plant material is important for plants such as Pelargonium sidoides DC used for production of phytomedicines that are available in local and international markets. There is limited research on how agronomic factors affects phytochemicals in P. sidoides roots.

Objective: To evaluate the effect of different irrigation regimes and harvesting age on metabolite accumulation in dried roots of P. sidoides.

Methodology: Irrigation was applied at 75%, 50% and 25% plant available water (PAW) corresponding to well- watered, moderate water deficit and severe water deficit respectively. P. sidoides, which were harvested at 6, 12 and 18 months after imposing the different water deficit treatments, roots dried and subjected to ultra-performance liquid chromatography -quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) coupled with multivariate statistical analysis.

Results: Unsupervised multivariate analysis showed that irrigation did not affect the obtained metabolic features. Orthogonal partial least squares discriminant analysis (OPLS-DA) showed statistically significance difference between 6 versus 12- and 18- months harvest ages. Compounds such as umckalin, epigallocatechin dimer, and gallic acid were increased in 12 and 18 months compared to the 6 months harvest. Sucrose/trehalose was increased by 0.2431- and 0.560- fold in 6 months compared to 12- and 18-months harvest ages respectively. On quantification, umckalin increased from 260.40 mg/kg DW at 6 months to 431.61 mg/kg DW at 12 months, while epigallocatechin rose from 342.98 mg/kg DW to 505.58 mg/kg DW over the same period. Umckalin sulphate was highest at 6 months under 25% PAW (7110.32 mg/kg DW) and decreased at 12 months harvest under the same irrigation level (4522.05 mg/kg DW).

Conclusion: The results indicated that younger plants accumulated more primary metabolites and modified secondary metabolites, whereas older plants accumulate more secondary metabolites. Moreover, cultivation of P. sidoides in limited water is plausible.