In Vitro Production of Plant Secondary Metabolites: Validated Platforms and Emerging Opportunities in Tropical and Subtropical Plant Species

Plant in vitro culture has emerged as a biotechnological approach for the sustainable production of high-value secondary metabolites. Despite advances in plant tissue culture and phytochemical research, converting biologically productive in vitro systems into reliable production platforms remains a major challenge because metabolite production alone does not necessarily reflect technological maturity. This review evaluates plant in vitro production platforms for secondary metabolites in tropical and subtropical plant species by distinguishing validated, partially validated, and emerging platforms according to their level of technological development. To support this assessment, we propose a technological validation framework based on complementary experimental evidence that distinguishes species-level scientific knowledge from platform-level technological validation. The analysis reveals substantial differences in platform development and identifies production reliability as the principal limitation preventing many systems from reaching more advanced stages of technological maturity. These findings indicate that technological maturity should be understood as a progressive process driven by the accumulation of complementary experimental evidence rather than isolated experimental achievements. Future advances in plant in vitro production will depend on integrating mechanistic understanding of secondary metabolite biosynthesis with process engineering approaches to develop robust, reproducible, and scalable production platforms, thereby facilitating the sustainable biotechnological exploitation of tropical and subtropical plant biodiversity.