Fabaceae is one of the largest plant families consisting of about 730 genera and 14,900 species identified to date [1]. The genus Dalbergia belongs to the Faboideae sub-family and consists of 274 species distributed across the globe [2] [3]. Most of the species from this genus are timber trees including Dalbergia lanceolaria, the plant investigated here. It is tall deciduous tree distributed in Bangladesh, Bhutan, India, Sri Lanka, Myanmar, Thailand, Cambodia, Vietnam and Pakistan [2]. Its root bark is used by local population for dyspepsia and the leaves are used for skin disorders such as leprosy [4]. Oil extracted from its seeds is used for rheumatic and skin disorders [5].

Multiple studies have evaluated the biological activities of D. lanceolaria extracts and provided proof of anti-inflammatory, analgesic, and anti-diarrheal activity [4] [5] [6]. Only one study is available which investigated chemical constituents from the root barks and identified a new glycoside—namely Lanceolarin [7]. A large number of compounds have been identified from various other species of Dalbergia genus. Flavonoids were the most common type of compounds isolated, and some terpenes have also been identified [2] [8]. However, no alkaloid has been reported to date. Among the terpenes, triterpenes and sesquiterpenes are common but diterpenes have not been reported.

Compound 1 (Figure 1) was obtained as a yellowish amorphous powder. The molecular formula was determined to be C₂₀H₂₂O₇ from NMR data. The ¹H NMR spectrum (Figure 2) of 1 showed peaks at peaks at δ_H 6.65, 7.70, and 7.75 which is indicative of protons in a furan ring. This spectrum also showed peaks at δ_H 3.93 and 3.63 indicating H-2 and H-3 in an epoxide ring. Singlet peaks at δ_H 1.11 and 1.04 were deduced to be from the two methyl groups (Me-18 and Me-20) and peak at δ_H 5.00 was deduced to be from H-1 near the ether bridge. The complete structure was elucidated by the combination of ¹H NMR, ¹³C NMR, DPT-135, ¹H-¹H COSY, HMBC data and was found to be in agreement with those reported for Jateorin [10] [11].

Compound 2 (Figure 3) was obtained as yellow crystalline solid. The molecular formula of this compound was determined to be C₂₀H₂₂O₆ from the NMR data. Similar to 1, the spectrum showed peaks at δ_H 6.46, 7.46, and 7.50 indicating presence of a furan ring. Singlet peaks at δ_H 1.28 and 1.10 corresponds to methyl groups. Presence of an ether bridge was indicated by a doublet peak at δ_H 5.18 corresponding to H-1. The complete structure was elucidated by evaluating ¹H NMR (Figure 4) and ¹³C NMR data. The data was in agreement with previous literature reporting Columbin [12].

Compound 3 (Figure 5) was obtained as colorless needle-shaped crystals. ¹H NMR spectrum (Figure 6) showed peaks at δ_H 3.51 (m, 1H), 5.34 (t, 1H), 0.92 (d, 3H, J = 6.48), 0.81 (d, 3H, J = 6.12), 0.785 (d, 3H, J = 6.54), 0.67 (s, 3H), 0.998 (s, 3H). The structure was elucidated from this data and was compared with previous literature reporting β-sitosterol [13]. Compound 4 (Figure 7) was white amorphous powder. ¹H NMR spectral data (Figure 8) from this compound gave peaks at δ_H 3.18 (dd, 1H), 2.36 (m, 1H), 1.91 (m, 1H), 0.94 (s, 3H), 0.75 (s, 3H), 0.82 (s, 3H), 1.02 (s, 3H), 0.91 (s, 3H), 0.77 (s, 3H), 4.56 (m, 1H), 4.68 (m, 1H), and 1.67 (s, 3H). This data was in agreement with those reported for Lupeol [14].

Both β-sitosterol and Lupeol have been previously reported from D. hainanensis, D. latifolia, D. ecastophyllum, and D. miscolubium [8] [15] [16] [17]. In addition, β-sitosterol has been isolated from other species of Dalbergia genus such as D. rubiginosa, D. volubilis, D. sissoides, and D. sissoo [18] [19] [20] [21].

Furanoditerpenes are found in various plants within the Fabaceae family [22] [23] [24] [25]. However, diterpenes have not been reported for Dalbergia genus except for some Gibberelins identified in D. dolichopetala [26]. Compound 1 (Jateorin) and Compound 2 (Columbin) are furanoditerpenes which is a novel finding for this genus. To the best of the authors’ knowledge, furanoditerpenes have never been reported in any publication for this genus. So, this finding is very interesting with respect to the phytochemistry of this species and the genus as a whole. Furthermore, all four compounds are being reported for the first time for D. lanceolaria.

In this present study, four compounds namely Jateorin, Columbin, β-sitosterol, and Lupeol were isolated from the methanolic extract of stem bark of D. lanceolaria. Among them, β-sitosterol and Lupeol are triterpenes and have been reported from other species within this genus. However, Jateorin and Columbin have not been reported previously from this genus. Hence, it is the recommendation of the authors that a systematic search be initiated to evaluate the presence of furanoditerpenes in other species within the Dalbergia genus.

The authors acknowledge that this investigation was funded by National Science and Technology Fellowship, Ministry of Science and Technology, People’s Republic of Bangladesh.

The authors declare no conflicts of interest.

Sultana, S., Tareq, F.S., Rahman, K.M. and Hasan, C.M. (2019) Isolation of Two Furanoditerpenes and Two Triterpenes from the Stem Bark of Dalbergia lanceolaria L.f. Pharmacology & Pharmacy, 10, 519-527. https://doi.org/10.4236/pp.2019.1012043