A polysaccharide (EOP) from Epiphyllum oxypetalum (DC.) Haw. was isolated and identified, and its immunomodulatory activity was evaluated both in vitro and in vivo . By using multispectral analysis, EOP was determined to be composed of rhamnose , arabinose , galactose , and galacturonic acid at a molar ratio of 26.65:11.48:53.79:6.04, and its molecular weight was 5.77 × 10 6 Da. In addition, backbone structure of EOP was determined to consist of (1 → 4)-linked β-Gal p , (1 → 2)-linked β-Rha p , (1 → 3,4)-linked β-Gal p , (1 → 2,4)-linked β-Rha p and (1 → 4) -linked α-Gal p A, terminating with t-β-Ara p and t-β-Gal p . The in vitro immunomodulatory activity assay on RAW 264.7 cell showed that EOP increased the proliferation of macrophages, enhanced its phagocytic capability, and promoted the production of cytokines including nitric oxide (NO), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6). Furthermore, the in vivo evaluation on zebrafish showed that EOP could reduce the residual content of fluorescent microspheres in zebrafish, which indicated that EOP had the capability to enhance the macrophage phagocytosis . All results suggested that EOP showed a complex structure and exhibited significant immunomodulatory activity both in vitro and in vivo that had the potential to be utilized valuably in food and medicine industries.
Epiphyllum oxypetalum, a renowned ornamental species in Cactaceae, releases attractive fragrance during its infrequent, transient and nocturnal blooms. However, the floral fragrance composition and biosynthesis remain largely unexplored. Employing volatilomics, transcriptomics and biochemistry, we systematically characterized the composition, emission dynamics and biosynthesis of the floral scent of E. oxypetalum. The floral scent composition of E. oxypetalum was highly dynamic. Starting after 20:00 local time, volatile emission increased 200-fold within six hours. At full bloom, geraniol accounted for 72.54% of the total emission, followed by benzyl alcohol (12.96%) and methyl salicylate (3.75%). These scents predominantly originated from petals and sepals. Transcriptomic analysis and inhibition assays using pathway-specific inhibitors revealed that the mevalonate pathway was the precursor source for geraniol biosynthesis. Functionally characterized cytosol localizing geraniol synthase EoTPSa1 was the key enzyme responsible for geraniol biosynthesis. Together, these findings pinpointed a cytosolic biosynthetic route for the major scent volatile geraniol in E. oxypetalum. Our study provides new insights into the emission dynamics and biosynthesis of E. oxypetalum floral scents. In particular, we demonstrated a distinctive mevalonate pathway-based geraniol biosynthetic pathway, which may hold potential for the development of novel perfume products.
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