The plant material, Dendrobium lindleyi Steud, was collected from the hilly regions of Bangladesh. Specimens were authenticated by a botanist, and voucher specimens (Accession No. DL-001) were deposited at the herbarium of the Department of Pharmacy, University of Dhaka.
The qualitative phytochemical screening of the leaf, stem, and root extracts of D. lindleyi was carried out using standard procedures [12, 13]. Various tests were performed to identify the presence of alkaloids, coumarins, cardiac glycosides, glycosides, flavonoids, proteins, phenols, quinines, resins, steroids, saponins, tannins, and terpenoids.
Quantitative analysis of selected phytochemicals was performed using spectrophotometric methods. Alkaloids were quantified by the colorimetric method using Dragendorff’s reagent . Total phenolic content was determined using the Folin-Ciocalteu method . The total flavonoid content was assessed using the aluminum chloride colorimetric assay . Tannins were quantified using the Folin-Denis method , and total protein content was determined by the Bradford assay .
Antioxidant Activity The antioxidant activity of the leaf, stem, and root extracts was evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay . The concentration of each extract required to scavenge 50% of the DPPH radicals (IC50) was determined.
The anti-inflammatory activity of the extracts was determined by the inhibition of protein denaturation method . Different concentrations of the extracts were tested, and the IC50 values were calculated.
Thrombolytic activity was assessed using a modified clot lysis assay . Different concentrations of the extracts were tested for their ability to lyse blood clots, and the IC50 values were determined.
Statistical analysis was performed using SPSS software. Correlation analysis was carried out to determine the relationship between phytochemical content and bioactivity. A p-value of less than 0.05 was considered statistically significant.
Qualitative Phytochemical Screening
The qualitative screening of D. lindleyi extracts revealed the presence of a diverse range of bioactive compounds, including alkaloids, coumarins, cardiac glycosides, glycosides, flavonoids, proteins, phenols, quinines, resins, steroids, saponins, tannins, and terpenoids. These compounds were present in varying amounts in the leaf, stem, and root extracts.
The quantitative analysis showed that the highest concentration of alkaloids (172.15 ± 1.22 mg/g) was found in the leaves, while the root had the highest levels of phenols (203.55 ± 0.75 mg/g) and flavonoids (24.35 ± 0.42 mg/g). Tannins were most abundant in the leaves (105.06 ± 0.55 mg/g), and proteins were most concentrated in the root (194.12 ± 0.65 µg/ml).
The root extract exhibited the highest antioxidant activity with an IC50 value of 58.24 µg/mL. The stem extract showed the most significant thrombolytic activity with an IC50 of 242.74 µg/mL, while the leaf extract displayed the most potent anti-inflammatory activity with an IC50 of 61.79 µg/mL.
Statistical analysis revealed a significant positive relationship between alkaloids (r = 0.96) and tannins (r = 0.9) with antioxidant, anti-inflammatory, and thrombolytic properties. This indicates that higher concentrations of alkaloids and tannins were associated with increased bioactivity in these assays.
The study on Dendrobium lindleyi Steud highlights the rich phytochemical diversity present in different parts of the plant, including the leaves, stems, and roots. The qualitative phytochemical screening identified a wide array of bioactive compounds, suggesting its potential for medicinal use. Additionally, the quantitative analysis revealed the specific distribution of phytochemicals in the plant, with alkaloids being most abundant in the leaves, phenols and flavonoids in the roots, and tannins in the leaves.
The bioactivity assessment demonstrated that different parts of D. lindleyi possess distinct pharmacological properties. The root extract displayed potent antioxidant activity, while the stem extract exhibited strong thrombolytic potential, and the leaf extract showed remarkable anti-inflammatory activity. These findings provide valuable insights into the medicinal potential of D. lindleyi and support its traditional use in treating various ailments.
Moreover, the positive correlations between alkaloids and tannins with antioxidant, anti-inflammatory, and thrombolytic activities suggest that these phytochemicals may play a crucial role in mediating the observed bioactivities. Further research is warranted to isolate and characterize the specific compounds responsible for these pharmacological effects, paving the way for the development of new drugs and therapeutic interventions based on D. lindleyi. Overall, this study contributes to the growing body of knowledge on the medicinal properties of orchids and underscores their significance in traditional and modern medicine.