Quality Studies on Cynometra iripa Leaf and Bark as Herbal Medicines

Abstract

Cynometra iripa Kostel. is a Fabaceae species of mangrove used in traditional Ayurvedic medicine for treating inflammatory conditions. The present study aims to establish monographic botanical and chemical quality criteria for C. iripa leaf and bark as herbal substances and to evaluate their in vitro antioxidant potential. Macroscopic and microscopic qualitative and quantitative analyses, chemical LC-UV/DAD-ESI/MS profiling, and the quantification of key chemical classes were performed. Antioxidant activity was evaluated by DPPH and FRAP assays. Macroscopically, the leaf is asymmetrical with an emarginated apex and cuneate base. Microscopically, it shows features such as two-layered adaxial palisade parenchyma, vascular bundles surrounded by 3-6 layers of sclerenchyma, prismatic calcium oxalate crystals (5.89 ± 1.32 μm) along the fibers, paracytic stomata only on the abaxial epidermis (stomatal index-20.15), and non-glandular trichomes only on petiolules. The microscopic features of the bark include a broad cortex with large lignified sclereids, prismatic calcium oxalate crystals (8.24 ± 1.57 μm), and secondary phloem with distinct 2-5 seriated medullary rays without crystals. Chemical profile analysis revealed that phenolic derivatives, mainly condensed tannins and flavonoids, are the main classes identified. A total of 22 marker compounds were tentatively identified in both plant parts. The major compounds identified in the leaf were quercetin-3-O-glucoside and taxifolin pentoside and in the bark were B-type dimeric proanthocyanidins and taxifolin 3-O-rhamnoside. The total phenolics content was higher in the leaf (1521 ± 4.71 mg GAE/g dry weight), while the total flavonoids and condensed tannins content were higher in the bark (82 ± 0.58 mg CE/g and 1021 ± 5.51 mg CCE/g dry weight, respectively). A total of 70% of the hydroethanolic extracts of leaf and bark showed higher antioxidant activity than the ascorbic acid and concentration-dependent scavenging activity in the DPPH assay (IC₅₀ 23.95 ± 0.93 and 23.63 ± 1.37 µg/mL, respectively). A positive and statistically significant (p < 0.05) correlation between the phenol content and antioxidant activity was found. The results obtained will provide important clues for the quality control criteria of C. iripa leaf and bark, as well as for the knowledge of their pharmacological potential as possible anti-inflammatory agents with antioxidant activity.

Keywords: Cynometra iripa; antioxidant; chemical profile; herbal substance; light microscopy; macroscopic analysis; mangrove species; quality control.

Figure 1

Cynometra iripa (a) general aspect; (b) fresh green leaf; (c) fresh bark.

Figure 2

C. iripa leaf macroscopic characters. (a) dried leaflet; (b) abaxial and adaxial view of the asymmetrical leaf. Scale bars: (a,b) = 1 cm.

Figure 3

C. iripa leaf macroscopic characters. Details of (a) adaxial and (b) abaxial view of emarginated apex; (c) cuneate base, petiolules, and rachis; (d) hairy petiolule. Scale bars: (a–c) = 5 mm; (d) = 2 mm.

Figure 4

C. iripa dried leaf. (a,b) LM micrographs of transverse section. Details of central vein and mesophyll; (c) adaxial surface without stomata; (d) abaxial surface with paracytic stomata; (e) calcium oxalate prismatic crystals at the vein; (f) unicellular trichomes on petiolule; xy—xylem, ph—phloem, sc—sclerenchyma, ade—adaxial epidermis, pp—palisade parenchyma, abe—abaxial epidermis. Scale bars: (a) = 100 µm; (b–f) = 50 µm.

Figure 5

C. iripa powdered leaf. Details of (a) fragments of epidermal cells and palisade parenchyma; (b) fibers; (c) free prismatic calcium oxalate crystals; (d) unicellular non-glandular trichome. Scale bars: (a–d) = 50 µm.

Figure 6

C. iripa bark macroscopic characters. Details of (a) adaxial view; (b) abaxial view. Scale bars: (a,b) = 1 cm.

Figure 7

Microscopic characters of C. iripa bark. Details of (a–d) transverse section of bark showing lenticel (le), periderm (pe), phelloderm (phe), and cortex; layer of thick sclereids (scl) and parenchyma cell (pa); a group of sclereids (scl); medullary rays (med) with 2–5 cell layers in secondary phloem; longitudinal sections (e,f) showing fibers (fb), calcium oxalate prismatic crystals (pc), starch granules (stg), at parenchyma (e); calcium oxalate prismatic crystals (pc) associated with fibers (f). Scale bars: (a) = 200 µm; (b,d,e) = 100 µm; (c,f) = 50 µm.

Figure 8

C. iripa powdered bark. Details of (a) fragments of fibers; (b) fragments of parenchyma (pf) and periderm (pef); (c) scattered calcium oxalate prismatic crystals (pc); scale bars: (a–c) = 50 µm.

Figure 9

LC/MS chromatographic profile of main marker compounds in C. iripa leaf (CIL) and C. iripa bark (CIB).

Figure 10

Major identified compounds from leaf (a,b) and bark (c,d) hydroethanolic extracts.

Figure 11

Scavenging activity of C. iripa leaf (CIL) and C. iripa bark (CIB) extracts; ASC-ascorbic acid.

Figure 12

The ferric reducing capacity of C. iripa leaf (CIL) and C. iripa bark (CIB) extracts; ASC-ascorbic acid.

Figure 13

Map of Bangladesh showing plant collection area in the Sundarbans mangrove forest; ca.1—collection area 1: Koromjol and ca.2—collection area 2: Harbaria eco-tourism center, Bangladesh.