## 6 Pharmacological Properties of _Apium_ Plants
### Antioxidant Activities of Apium Plants  
Flavonoid and phenolic compounds are mostly responsible for the antioxidant activity and they are abundantly found in plants such as _Apium_ plants. Many studies have been carried out to demonstrate the antioxidant activity of _Apium_ plants both in vitro and in vivo. Many studies reported the antioxidant activity of _Apium_ plant seeds, roots, and leaves. _A. gravelens_ leaves contain approximately 202 mg/kg flavonoid with 48 mg/kg luteolin and 27 mg/kg chrysoeriol 7-glucosidase [157]. [PERSON] et al. extracted the phenolic compound of _A. gravelens_ leaves with methanol, partitioned water, ethyl acetate, butanol, and the phenolic contents were determined by Folin-Coicalteu method. In addition, they determined some antioxidant activity in vitro models such as antioxidant capacity by radical scavenging activity using DPPH (\(\alpha\), \(\alpha\)-diphenyl-\(\beta\)-picrylhydrazyl), \(\beta\)-carotene-linoleate, reducing power, metal chelating effects, and the phosphomolybdenum method [113]. They showed that the highest phenolic content of the extracts was established in methanol (51.09 mg/g) followed by water extract (46.40 mg/g), ethyl acetate (22.70 mg/g), and butanol extract (19.43 mg/g). In addition, they found that methanol extract had the highest free-radical scavenging capacity followed by water, ethyl acetate, and butanol extract. Their results showed that _A. gravelens_ leaves are rich in phenolics and are a good source of antioxidants [113; 119]. In another study, [PERSON] et al. evaluated the total antioxidant capacity of _A. gravelens_ leaves using CUPRAC (cupric ion reducing antioxidant capacity) and ABTS (2,2-azino-bis [3-ethyl-benzothazoline-6-sulfonate]) methods and they also determined the phenolic compounds with high-performance liquid chromatography (HPLC) [158]. Caffeic acid, p-coumaric acid, and ferulic acid were determined as major phenolic acids, and apigenin, luteolin, and kaempfer were determined as major flavonoids [119; 158].  
The antioxidant activity of _A. gravelens_ was investigated by [PERSON] et al. [154]. They also indicated that the total phenolic content was higher in methanolic fraction (63.46 mg GAE/g) followed by ethanol (36.60 GAE/g), and hexane fractions (34.86 mg GAE/g). Similarly, the flavonoid content was high in methanolic extract (56.95 quercetin/g). In addition, they showed antioxidant activity with FRAP assay with 12.48 mM FeSO\({}_{4}\) equivalent/L in methanolic fraction [150; 154]. The DPPH radical scavenging capacity of the essential oil from the _A. gravelens_ leaves was investigated and the results indicated that the essential oil from _A. gravelens_ has potential as a natural antioxidant, and thus inhibited the oxidation process [159]. In another study, eleven cultivars of celery were analyzed for their antioxidant activities. Among these eleven cultivars, Shengjie celery had the highest antioxidant activity, whereas, Tropica had the lowest. An extremely significant positive correlation between the antioxidant activity and the contents of total flavonoids, total phenolic acids, or total phenolics was observed in this study. The _A. gravelens_ species displayed high antioxidant capacity and high free-radical scavenging activities [134].  
[PERSON] et al. investigated the antioxidant activity of celery in rats treated with doxorubicin and also the effect of the celery itself, and its combination with doxorubicin was determined by its antioxidant status [160]. The _n_-butanol extract from _A. gravelens_ seed at 60 mg/kg ameliorate lipid peroxidation and its antioxidant properties improved antioxidant enzymes in streptozotocin-induced diabetic rats after 21 days of treatment [26].