Pharmacognostic evaluation of some plants from the Zingiberaceae family

The utilization of medicinal plants for promoting health, preventing diseases, supporting therapeutic interventions, and enhancing both the quality and longevity of life has been steadily increasing. Among these, members of the Zingiberaceae family hold significant pharmacological and ethnobotanical importance. Rhizomatous species within this family commonly consumed as spices or herbal teas in daily life are also extensively incorporated into cosmetic formulations and dietary supplements. Notable representatives of this family include Curcuma longa L., Zingiber officinale Roscoe, Alpinia officinarum Hance, and Elettaria cardamomum (L.) Maton. This study aims to evaluate the antioxidant potential and phytochemical composition of these species by assessing their radical scavenging capacity key indicators of antioxidant activity and comparing both interspecies variation and differences among various extracts derived from the same species. To this end, extracts were prepared using solvents of varying polarity, namely water, ethanol, dichloromethane/chloroform, and ethyl acetate. The antioxidant activities of the extracts were quantitatively analyzed using DPPH and ABTS assays, alongside determination of total phenolic and flavonoit contents through spectrophotometric methods. Based on the obtained data, the ethyl acetate extract of Alpinia officinarum (galangal) exhibited the highest total phenolic content among all extracts, with a value of 311,52 ± 68,59 mg GAE/g. In contrast, the lowest phenolic content was found in the aqueous extract of the same plant, measured at 3,41 ± 2,85 mg GAE/g. Regarding flavonoid content, the highest value was determined in the chloroform extract of Curcuma longa (turmeric), with 83,70 ± 0,79 mg QE/g, while the lowest value was observed in the ethanol extract of Zingiber officinale (ginger), at 1,89 ± 0,43 mg QE/g. In this study, the antioxidant activities of extracts obtained with different solvents were evaluated using DPPH and ABTS radical scavenging assays. IC₅₀ values were calculated to quantitatively compare the radical scavenging capacities of each extract, and ascorbic acid and BHA were used as reference standards in DPPH and ABTS methods, respectively. According to the DPPH assay results, Alpinia officinarum showed the highest antioxidant activity, particularly in its ethyl acetate extract (IC₅₀: 116.51 ± 53.22 μg/mL), followed by Zingiber officinale extracts with moderate activity. Curcuma longa exhibited weaker activity, while Elettaria cardamomum failed to reach 50% inhibition in this method. In the ABTS assay, the strongest activity in the ethyl acetate extract of Zingiber officinale (IC₅₀: 66,32 ± 1.80 μg/mL), followed by Alpinia officinarum. Cardamom again demonstrated the weakest antioxidant potential. These findings suggest that Alpinia officinarum and Zingiber officinale are promising natural sources of antioxidants. The observed activity differences highlight the influence of extraction solvent and phytochemical composition on antioxidant efficiency. In addition, microscopic evaluations were conducted to support phytochemical findings with morphological evidence. The findings of this thesis are expected to provide a more comprehensive understanding of the bioactive profiles of Zingiberaceae species across different solvent systems, thereby contributing valuable data to the scientific literature in the fields of pharmacognosy, phytochemistry, and natural product research. xi Keywords: Zingiberaceae, ginger, cardamom, turmeric, galangal, free radical scavenging activity