New Diterpenoids from Clerodendranthus spicatus

Two new diterpenoids, neoorthosiphonones B and C (1 and 2), and one known diterpenoid, were isolated from the aerial parts of Clerodendranthus spicatus. Their structures including absolute configurations were determined by comprehensive spectroscopic analyses and X-ray crystallographic methods. No compound was found to inhibit fibronectin production at the concentration of 20 μM. Electronic supplementary material The online version of this article (doi:10.1007/s13659-017-0128-8) contains supplementary material, which is available to authorized users.


Results and Discussion
Analysis of the HRESIMS at m/z 715.2515 [M?K] ? (calcd for C 38 H 44 O 11 K, 715.2515), 13 C NMR, and DEPT data of neoorthosiphonone C (2) indicates that 2 has the same molecular formula and similar structure as does 1.  (Fig. 3), unambiguously assigning the relative configuration of 2. In the same manner as that of 1, the double bond between C-13 and C-15 was deduced to be Z-form due to ROESY correlation of H-15/H 3 -17. As a result, the structure of 2 was identified and named as neoorthosiphonone C.
So far, diterpenoids with several frameworks have been characterized from the title species [1]. Compounds 1 and 2 are characteristic of the presence of a 6/6/8 ring system which makes it unusual despite that neoorthosiphonone A as the only one analogue has been identified from C. spicatus [12].
The known compound neoorthosiphonone A (3) was isolated and identified by comparing its spectroscopic data with those previously reported [12].
Considering that C. spicatus is commonly used for renal diseases, in this study, compounds 1-3 were evaluated for their roles in renal protection by targeting fibronectin production in TGF-b1-induced rat kidney tubular epithelial cells using the method reported previously [13]. However, no compound was found to inhibit fibronectin production at the concentration of 20 lM. Whether these compounds are active towards the other kidney associated targets needs further investigation.

General Experimental Procedures
Optical rotations were performed on a JASCO P-1020 digital polarimeter. UV spectra were obtained on a Shimadzu UV-2401PC spectrometer. NMR spectra were recorded on a Bruker Avance III 600 MHz spectrometer, with TMS as an internal standard. ESIMS and HRE-SIMS were measured on an API QSTAR Pulsar 1 spectrometer. C-18 silica gel (40-60 lm; Daiso Co., Japan), MCI Fig. 1 The structures of compounds 1-3

Extraction and Isolation
The air-dried powders of C. spicatus (15 kg) was extracted under reflux using 70% EtOH (3 9 60 L 9 2 h) to give a crude extract, which was suspended in water followed by successive extraction with petroleum ether and EtOAc.   (calcd for C 38 H 44 O 11 K, 715.2515); 1 H and 13 C NMR data, see Table 1.

Bioassay
All compounds were evaluated for their effects in renal protection as previously described methods [13].