Anti-inflammatory and antinociceptive effects of Curcuma kwangsiensis and its bioactive terpenoids in vivo and in vitro

“Curcumae Radix”, the dried rhizomes of Curcuma kwangsiensis documented in Chinese pharmacopoeia, has been traditionally used for the treatment of inflammatory and pain diseases, such as jaundice and red urine, cleaning the heart-fire and depression, arthralgia, and dysmenorrhea. However, according to literature surveys, anti-inflammatory and antinociceptive studies of C. kwangsiensis have been seldom reported so far. The current study focuses on the anti-inflammatory and antinociceptive effects of C. kwangsiensis and discovering the bioactive compounds for its traditional usages both in vivo and in vitro, which could provide scientific justification about its traditional use. The anti-inflammatory and antinociceptive assays of various layers (ME, EA, AQS) from C. kwangsiensis were achieved by carrageenan-induced paw edema and acetic acid-induced writhing animal models, respectively. The most bioactive part, EA layer was further phytochemically investigated by multiple step chromatography techniques. The structures of these isolates were unambiguously elucidated by means of extensive spectroscopic and chemical methods, and comparison with corresponding data of the reported literature. Four major sesquiterpenoids (4, 6, 14, and 15) were achieved for their anti-inflammatory and antinociceptive assays by the two aforementioned animal models in vivo. All the isolated compounds were evaluated for their anti-inflammatory effects via detecting inflammatory mediator releases (COX-2, IL-1β, and TNF-α) in RAW 264.7 macrophage cells induced by LPS. The ME and EA layers significantly alleviated the paw edema caused by carrageenan and decreased the number of writhes induced by acetic acid at the dose of 200 and/or 100 mg/kg in comparison to the control group (p < 0.01/0.05), and the EA layer exhibited better activity than that of ME layer. Subsequent phytochemical investigation on EA layer of C. kwangsiensis exhibited that three new terpenoid compounds (1–3), identified as (12Z,14R)-7β-hydroxylabda-8(17),12-diene-14,15,16-triol (1), (12Z,14S)- 7β-hydroxlabda-8(17),12-diene-14,15,16-triol (2), and (4S)-hydroxy-(8)-methoxy-(5S)-(H)-guaia1(10),7(11)-dien-12,8-olide (3), together with twenty-two known analogs were isolated. Furthermore, four major sesquiterpenoids (4, 6, 14, and 15) significantly relieved the paw edema and number of writhes at 100 and/or 50 mg/kg (p < 0.05/0.01). Likewise, the majority of sesqui- and diterpenoids isolated could remarkably inhibited the secretion of inflammatory mediators (COX-2, IL-1β, and TNF-α) in LPS-stimulated RAW 264.7 macrophages cells at the concentration of 20 μg/mL, comparable to DXM used as the positive control. All the results suggested that EA layer from C. kwangsiensis possessed the anti-inflammatory and antinociceptive activities, and these sesqui- and diterpenoids could be the effective constituents responsible for relieving inflammation. The present studies undoubtedly determined the anti-inflammatory and antinociceptive material basis of C. kwangsiensis, including the EA layer and its precise components, which presented equivalent or better anti-inflammatory effects than that of positive control (ASP/DXM) in vivo and in vitro. These results not only would account for scientific knowledge for traditional use of C. kwangsiensis, but also provide credible theoretical foundation for the further development of anti-inflammatory and antinociceptive agents.