A New Antimalarial Noreudesmane Sesquiterpenoid from Dobinea delavayi.

One previously undescribed angeloylated noreudesmane sesquiterpenoid, dobinin O (1), along with four known eudesmane sesquiterpenoids (2-5) were isolated from the peeled roots of Dobinea delavayi. Their structures were elucidated by extensive spectroscopic data analyses. In addition, compound 1 exhibited moderate antimalarial activity against Plasmodium yoelii BY265RFP with the inhibition ratio of 17.8 ± 13.3% at the dose of 30 mg/kg/day.


Introduction
Dobinea delavayi (Baill.) Baill. is a perennial herb with purple-brown, cylindrical and bulky roots, which is distributed in Yunnan and Sichuan provinces of China at the altitude from 1100 to 2300 m [1]. The shape of processed roots of D. delavyi likes a sheep's horn. Therefore, D. delavyi is called "Yang-Jiao-Tian-Ma" in China, and used to treat cough due to heat in the lung, traumatic injury, mumps, mastitis, sores, furuncles, and so on, in the folk [2].
Compound 1 was evaluated for its in vivo antimalarial activity against Plasmodium yoelii BY265RFP in mice, according to a four-day suppressive test [3]. As shown in Table 2, compound 1 exhibited moderate antimalarial activity with the inhibition ratio of 17.8 ± 13.3% at the dose of 30 mg/kg/day. This was further confirmed by the features of relief of hepatomegaly, increase of number of erythrocyte and content of hemoglobin, and recovery of abdominal temperature when the infected mice were treated with compound 1 (Tables S1-S3, Supporting Information). Furthermore, the immunomodulatory effect of compound 1 on the host response was also evaluated by the levels of splenic CD4 + CD25 + regulatory T cells

Plant Material
Dried and peeled roots of Dobinea delavayi (Baill.) Baill. were purchased from the herbal medicine market

Extraction and Isolation
The roots of D. delavayi (1.1 kg) was extracted with 80% ethanol at room temperature (5 × 10 L, each for 24 h), and the extract solutions were combined and concentrated under reduced pressure. Subsequently, the resulting residue (180 g) was suspended in water and partitioned with ethyl acetate.

Antimalarial Activity
The antimalarial assay was performed according to a fourday suppressive test as we previously described [3].