(+/−)‐Alashanoid N, Two Enantiomeric Sesquiterpenes from Syringa pinnatifolia

Abstract

Two enantiomeric humulane sesquiterpenes, namely (+)‐alashanoid N (1a) and (−)‐alashanoid N (1b), along with two known analogs ((2R,3R,5R)‐2,3‐epoxy‐6,9‐humuladien‐5‐ol‐8‐one (2) and (2R,3S,5R)‐2,3‐epoxy‐6,9‐humuladien‐5‐ol‐8‐one (3)), were described from the peeled stems of a folk Mongolian herbal medicine Syringa pinnatifolia. Their structures were characterized based on UV, IR, NMR, and HR‐ESI‐MS data analyses, and the absolute configurations were determined by data analysis of X‐ray diffraction and quantum chemical calculations. (+/−)‐Alashanoid N showed inhibition against NO production in RAW 264.7 macrophage cells with IC50 values of 90.1 μM and 71.7 μM, and protective effect against oxygen‐glucose deprivation injury to H9c2 cells at a concentration of 20 μM and 5 μM, respectively.

Metabolome and transcriptome analyses identify the plant immunity systems that facilitate sesquiterpene and lignan biosynthesis in Syringa pinnatifolia Hemsl.

“…According to recent studies, many new sesquiterpenes and lignans have been identified in S. pinnatifolia [ 8 , 39 , 40 ]. Therefore, this woody plant is a valuable resource for discovering new compounds, especially sesquiterpenes and lignans, which may be regarded as potentially important chemicals in the development of medicines because of their abundance in S. pinnatifolia [ 4 ].…”

Syringenes M – Q, Eremophilane Sesquiterpenoid Dimers from the Peeled Stems ofSyringa pinnatifolia

“…There were a few eremophilane dimers reported from several genera such as Ligularia, [18 -20] Incarvillea, [21] and Eremophila, [22] but none has been described in Oleaceae except for syringenes AÀ L from SP. [15] Therefore, compared to humulane such as zerumbone, and alashanoids AÀ S, [9,11,12,14] dimeric eremophilane might serve as a more characteristic chemical marker to distinguish SP from other Syringa species, which provides another chemical evidence to support the classification controversy for previous methods. [23]…”

“…The extraction and fractionation procedures were previously reported [12] . Briefly, the powdered and air‐dried peeled stems (20 kg) of S. pinnatifolia were extracted with EtOH under reflux with 95 % and 80 % (25 L, each 1.5 h).…”

“…Previous studies revealed that terpenoids in particular sesquiterpenoids are the most representative constituents of SP, [10–14] and more than 10 types of sesquiterpenoids have been described from SP so far, including humulane, eremophilane, caryophyllane, and pinnatane, which are specific constituents used to distinguish SP from other Syringa species. However, no dimeric sesquiterpenoid was discovered in the genus until our recent report of dimeric eremophilanes syringenes A−L from SP, which focus on the bioactivities and mechanisms of antitumor effect [15] .…”

Alashanoids O–S, seco‐Humulane and Eremophilane Sesquiterpenoids from Syringa pinnatifolia

“…Previously, our group reported a series of sesquiterpenoids with diverse types from SP, such as humulane, caryophyllane, eremophilane, and recent discovered syringane and pinnatane, [7–11] and found that many sesquiterpenoids from SP exit as racemates, which provided inspiration for the potential unusual biosynthesis of sesquiterpenoids within this species. In order to discover new and more biological sesquiterpenoids, a continued phytochemical investigation was performed on the terpenoid‐enriched portion, guided by 1 H‐NMR spectroscopic data of SP fractions, which led to the isolation of five new sesquiterpenoids ( Figure 1), namely alashanoids O–S ( 1 – 5 ), including two seco‐humulanes with a rare 13‐membered oxygen heterocycle framework and three eremophilane ones, along with three known analogs ( 6 – 8 ).…”