Nervilia fordii (Hance) Schltr. has been widely used as a medicinal and edible herb in Southwest China and Southeast Asia. In this study, NFP-1, a new water-soluble polysaccharidewith a purity of 97.8%, was purified from water extract of Nervilia fordii by DEAE-cellulose and Sephadex G-100 chromatography. NFP-1 has a relative molecular weight of 950 kDa determined by high performance gel-permeation chromatography (HPGPC). Its monosaccharide compositions were analyzed by high performance liquid chromatography (HPLC) after pre-column derivatizing its hydrolysate with 1-phenyl-3-methyl-5-pyrazolone (PMP). NFP-1 mainly consists of galactose, arabinose, rhamnose, and galacturonic acid. Based on FT-IR, methylation and GC-MS analysis, and NMR, the structure unit of NFP-1 was established as →4)-α-Rhap-(2→ 4)-α-GalpA-(1→2)-α-Rhap-(1→2)-α-Rhap-(4→1)-β-Galp-T containing two branch chains of →2,4)-α-Rhap-(1→5)-α-Araf-(1→3)-α-Araf-(1→, and →2,4)-α-Rhap-(1→4)-β-Galp-(1→. The immunomodulatory assays revealed the dual-functionalities of NFP-1. NFP-1 could significantly induce the secretion of nitric oxide (NO), and promote the secretions of TNF-α, IL-6, and IL-1β in RAW264.7 macrophages. NFP-1 could also significantly inhibit the production of NO, depress the secretions of TNF-α, IL-6 and IL-1β in RAW264.7 macrophages activated by lipopolysaccharide (LPS), and promote the production of IL-10 meanwhile. Our study suggested that Nervilia fordii could be an ideal medicinal or functional food due to its dual immunomodulatory activities.

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Five new flavonoid glycosides, namely nervilifordins F-J (1-5), were isolated from the 60% EtOH extract of the aerial parts of Nervilia fordii, along with three first isolated flavonoids (7, 8, and 13) and five known flavonoids (6, 9-12). The structures of new compounds were elucidated on the basis of 1D and 2D NMR and MS studies. Their anti-inflammatory activities were tested by measuring their inhibitory effects on nitric oxide production in lipopolysaccharide-activated RAW264.7 macrophages. Compounds 2 and 5 showed interesting inhibition effects with their EC50 values of 15.15 μM and 14.80 μM, respectively.

Flavonoid glycoside is commonly found in natural plants, possesses diverse bioactivities and potential medicinal values, and its synthesis methods are worthy to be studied. The synthesis of flavonoid glycosides covering the literatures from 2014 to 2018 is reviewed. The flavonoid glycoside synthesis includes two major methods of chemosynthesis and biosynthesis. Chemosynthesis includes total synthesis and semi-synthesis. The total synthesis has two classical methods of the Baker-Venkataraman (BK-VK) reaction and the Algar-Flynn-Oyamada (AFO) reaction. The semi-synthesis is usually starting from natural flavonoid, such as rutin, quercetin, kaempferol, naringenin and so on. Moreover, the chemosynthesis of flavonoid O-glucoside has three prime methods, Koening-Knorr method, phase transfer catalysis method, and glycosyl trichloroacetimidate method. As for the chemosynthesis of flavonoid C-glycoside, its glycosidic linkage is mainly completed via the O→C rearrangement reaction. Currently, the glycosyltransferase and glycosynthase are usually employed in the enzyme-catalyzed biosynthesis of flavonoid glycosides.

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