Cinnamoyl Derivatives from Cordia Platythyrsa and Chemiotaxonomical Value of the Cordia Genus

Phytochemical investigation of the roots and stem barks of Cordia platythyrsa (Boraginaceae) had led to the isolation of two new cinnamates, the cordicinnamate A compound 1 and the cordicinnamate B compound 2 along with four known compounds. Their structures were established by spectroscopic analysis mainly FAB and TOF –MS, H NMR and C NMR, COSY, HMBC, HSQC and by comparison with literature data. The cinnamoyl derivatives were reported for the first time in the Cordia genus. The isolation and identification of cinnamoyl derivatives in cordia genus improve the chemiotaxonomy value in this genus.


Introduction
The genus cordia belongs to the family of boraginaceae and it is found in warm regions [1]. The decoction of several species of cordia genus has been used in traditional medicine to treat influenza, fever, pneumonia, coughs, insomnia, stomach-ache, parasitic [2] and infections [3]. Previous phytochemical investigations of cordia genus led to the isolation of pyrrolizidine alkaloids, terpenoids flavonoids, lignans, meroterpenoids naphtoquinones [4]. In addition, phytochemical studies of Cordia platythyrsa have revealed the presence of shingolipids, Cordiachromes A-F [5] and xanthones [6]. Its leaves are used for the treatment of convulsions and sleeping sickness (maceration) [7]. With a view to extending the phytochemical investigations of these species, the present paper report the isolation and structure characterization of two new cinnamates namely cordicinnamate A-B and other known compounds.

General Experimental Procedure
Melting points were determined on a Büchi 434 melting point apparatus and were uncorrected. 1 H NMR (400 MHz) and 13 C NMR (150MHz) spectra were recorded at room temperature in CDCL 3 using a Bruker AVANCE AM 400 and AMX 500 NMR instruments. Chemical shifts are given in δ (ppm) value relative to TMS as internal standard. ESI-TOF mass spectra operating in positive mode were recorded on a finnigan MAT 312 and FAB mass spectra was recorded on Jeol JMS HX 110 mass spectrometer. Silica gel (230-400 meshes) and sephadex gel (LH-20) were used for Column Chromatography (CC) and vacuum liquid chromatography (VLC). Thin Layer Chromatography (TLC) was performed on precoated silica gel plates (60 F254, Macherey-Nagel) using the system solvent n-hexane -EtOAc (9.2:0.8, 8:2) and EtOAc-MeOH (6.5:3.5) as eluent. Spots were visualized by UV light (λmax = 254 nm, 366 nm) and were observed after using sulphuric acid (50%) as spraying reagent.

Plant Material
The stem barks and roots of Cordia platythyrsa were collected in Yaoundé town (Cameroon) and were identified by Dr N. Tsabang, of the Centre for Study of Medicinal Plants of Yaoundé (Cameroon). One voucher specimen (N⁰43625/HNC) was deposited at the National Herbarium of Cameroon (NHC).

Extraction and Isolation
The powdered roots (2 Kg) were extracted with CH 2 Cl 2 -MeOH (1:1) at room temperature for 72 hours. The resulting extract was evaporated to dryness under reduced pressure to yield a dark residue (12.72 g). This residue was partitioned with n-hexane, EtOAc and MeOH. The EtOAc extract was evaporated under reduced pressure to afford 8 g of residue. This residue was submitted to vacuum liquid chromatography (VLC) on silica gel 230-400 meshes eluted with n-hexane -EtOAc and EtOAc in order of increasing polarity. As result, 3 fractions (S1, S2 and S3) were collected on the basis of TLC. Fraction S3 was subjected to CC using silica gel 230-400 meshes eluted with n-hexane -EtOAc (9.2:0.8) afforded to 9 subfractions. Subfraction S375 was purified using sephadex gel LH-20 eluted with MeOH to afford compounds 1 (1.90 mg) and 5 (2 mg).

Identification of the Compounds
In addition, phytochemical studies on Cordia platythyrsa yielded to two news cinnamoyl derivatives, Cordicinnamate A (compound 1) and Cordicinnamate B (compound 2). To the best of our knowledge this is the first time that cinnamates have been reported from Cordia genus.

Conclusion
Phytochemical studies on Cordia platythyrsa yielded two cinnamoyl derivatives isolated for the first time on Cordia genus along with five others known compounds. To the best of our knowledge, this is the first time to isolate the cinnamoyl skeleton on the Cordia genus. The isolation and the identification of cinnamoyl derivatives in cordia genus improve the chemiotaxonomy value of the Cordia genus. Further studies aiming to isolate and identify compounds for the other fractions are needed.