###### Abstract  
Cultivated rice is a staple food for more than half of the world's population, providing approximately 20% of the world's food energy needs. A broad spectrum of pathogenic microorganisms causes rice diseases leading to huge yield losses worldwide. Wild and cultivated rice species are known to possess a wide variety of antimicrobial secondary metabolites, known as phytoalexins, which are part of their active defense mechanisms. These compounds are biosynthesized transiently by rice in response to pathogens and certain abiotic stresses. Rice phytoalexins have been intensively studied for over half a century, both for their biological role and their potential application in agronomic and pharmaceutical fields. In recent decades, the growing interest of the research community, combined with advances in chemical, biological, and biomolecular investigation methods, has led to a notable acceleration in the growth of knowledge on rice phytoalexins. This review provides an overview of the knowledge gained in recent decades on the diversity, distribution, biosynthesis, chemical synthesis, and bioactivity of rice phytoalexins, with particular attention to the most recent advances in this research field. Oryza; rice, phytoalexins; phytocassanes; oryzaeins; momilactones; skuranetin; pherilammides 20232260330  
production of pathogen cell wall-degrading enzymes, and accumulation of specialized toxic metabolites, including phytoalexins and phytoanticipins. The phytoalexin concept was first introduced by [PERSON], who observed that inoculation of potato plants with an incompatible strain of _Phytoplankton infestans_ induced the biosynthesis of a putative defense compound that conferred resistance to a compatible strain of this phytopathogenic comycete [5]. In 1940 [PERSON] and [PERSON] referred to phytoalexins as \"chemical compounds produced as a result of invasion of living cells by a parasite\" [6]. In the following years, it emerged that the biosynthesis of phytoalexins can also be induced by abiotic stress, such as exposure to UV radiation or heavy metal ions. Furthermore, increasingly sensitive analytical techniques showed that phytoalexins can be produced and/or accumulated even in healthy tissues, albeit at very low levels. Considering these observations, since the 1980s, a broader concept of phytoalexins gained acceptance from the scientific community: \"Products of higher plant metabolism, absent from healthy tissues or present only in negligible traces, which accumulate in significant amounts in response to fungal or bacterial challenge\" [7]. The concept of phytoanticipins was introduced in 1994 by [PERSON] and colleagues [8] with reference to \"low molecular weight antimicrobial compounds present in plants before challenge by microorganisms or produced after infection solely from pre-existing constituents\". According to the above definition, phytoalexins are mainly defined in terms of biosynthesis dynamics and biological role rather than in terms of chemical structure or biosynthetic origin. Indeed, phytoalexins can be biosynthesized through different pathways and thus belong to different classes of secondary metabolites, including terpenoids, phenols, and alkaloids. Sometimes, they are even structurally hybrid compounds whose biosynthesis involves the contribution of multiple biosynthetic pathways [9]. Some of rice's secondary metabolites, such as momilactone B, exhibit a significant inhibitory activity on seed germination and plant development in addition to playing a key role in plant-pathogen interactions (phytoalexins) and are, therefore, presumed to be involved in plant-plant antagonistic interactions (allelochemicals). The allelopathic activity of natural compounds is attracting growing interest in the research community, stemming from their potential to develop next-generation bioherbicides for use in sustainable weed management [10; 11; 12; 13]. In addition to being key components of the plant defense system, phytoalexins exhibit a wide range of health-promoting biological activities [14; 15].