## 1 Introduction  
Female hop cone infloreserences are frequently employed in the brewing industry. Around a strip (or central rachis) are petal-like structures on the hop cone called 'bracts' and 'bracteoles'. The glandular trichomes in the lupulin glands support female cones. This section biosynthesizes specific secondary metabolites, such as hop essential oil, hop polyphenols, and total resins, including hop bitter acid (\(\alpha\)- and \(\beta\)-acids) and prenylated flavonoids, particularly the xanthohumol derivatives. Hops' brewing value is primarily attributable to the precursors of flavor- and bitter-active compounds found in lupulin gland resins. The hop essential oils are particularly vital to the brewer as they provide flavor and aroma to the beer [1]. A total of 75 distinct samples from the global hop market were recently evaluated for 117 key bitter tastants using a multiparametric HPLC-MS/MS MRM technique [2]. Hop bitter compounds were identified as \(\alpha\)-acids and \(\beta\)-acids among the major flavour compounds characterized in the hop resin [3]. Notably, \(\alpha\)-acids are isomerized during the wort boiling process into the corresponding cis- and trans-iso-acids [4], which have been recognized as the major contributors to the bitter flavor of the beer. Polyphenols are responsible for the bitterness, color, body, and astringency of beer [5] and have been shown to impact beverage acceptability [6]. Flavonols, among the polyphenols, are of great significance to brewers since they generate protein-polyphenol complexes, which generate haze or turbidity in beer. They function as antioxidants in beer, mitigating oxidative degradation while also conferring possible health benefits on consumers by inhibiting the action of some mutagens and carcinogens [7]. Among the preynlated flavonoids, xanthohumol has received much attention due to its cancer preventive, anti-inflammatory, and antioxidant properties [8; 9; 10]. Hop essential oil rich in diverse terpen conferred hoppy taste to beer [11]. However, the findings mentioned earlier are confounded by genetic, environmental, and process-level heterogeneity [12], indicating that hops contribute a complex spectrum of flavor molecules to beer. Nonetheless, sensory evaluations of hop extract aroma and final beer taste and aroma have revealed two monoter compounds, linalool and geraniol, as key flavor drivers [13; 14]. The above-stated compounds are present from the start of cones development, and they continue to accumulate as the cones mature [1; 15; 16]. The genome draft of three hop cultivars was released in 2015 [17], revealing the developmental modulation of genes involved in specific metabolic pathways that influence beer taste and flavor. The accumulation sequence and metabolism of these compounds can be influenced by the hop cultivars, environment, and harvest time, etc. [12; 18; 19]. Importantly, the accumulation performance of these phytochemical compounds is related to the various functions of enzymes (synthase, isomerase, or transferase) involved in the biosynthesis pathway. With the development of craft beer, the application of hops and its three main photochemical components (hop bitter acids, polyphenols, and xanthohumol derivatives) remains to be extensively investigated. In-depth studies of the properties of the various phytochemical compounds have encouraged researchers to optimize their use in the beer brewing process. This has prompted individuals to focus on getting more of these essential compounds during upstream growth and preparing them via other techniques. Furthermore, the upstream fraction of the biosynthesis pathway of hop phytochemical compounds, regarded as a suitable tool for producing important functional components such as lycopene, artemisinin, and carotenoids, have promising applications in the treatment of diseases and improving human health. However, there has not been a systematic review to summarize the synthesis pathways or the rate-limiting reactions (enzymes) of these important compounds in hops.