# A Review on Bioactive Compounds and Pharmacological Activities of _Citrus unshiu_
## 4 Pharmacological Activities of Satsuma Mandarin
### Antioxidant Activity  
Numerous experiments have thoroughly assessed the antioxidant activity of _C. unshiu_ bioactives. In one experiment, the antioxidant activity of sunburned and non-sunburned fruits of _C. unshiu_ was evaluated. The peel and pulp of _C. unshiu_ were dried at 45 \({}^{\circ}\)C for two days, ground into powder, and then extracted by adding 30 mL of 70% ethanol to the powder. The extracts (hesperidin, narirutin, and naringin) exerted significant antioxidant activity in moderate-severe sunburned _C. unshiu_ compared to those in the non-sunburned (control). Sunburned fruits showed lower IC\({}_{50}\) values for diammonium salt (ABTS\({}^{+}\)) radical scavenging activity and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity than non-sunburned fruits, indicating a high level of antioxidant activity in _C. unshiu_[35]. The antioxidant activity of flavanones from _C. unshiu_ exposed to ozone treatment was determined using the DPPH and ABTS\({}^{+}\) methods. _C. unshiu_ peel was frozen in liquid nitrogen, powdered, stored at \(-\)80 \({}^{\circ}\)C, and then extracted with 70% methanol (10 mL). The DPPH activity of _C. unshiu_ peel extracts (hesperidin, narirutin, and naringin) was increased following exposure to ozone on day 1 (8.7%) and day 4 (8.5%). On the other hand,the ABTS\({}^{+}\) activity was increased on day 1 and day 4 by 4.2% and 2.1%, respectively [36]. The methanolic extracts of _C. unshiu_ peel during different stages of development were investigated for antioxidant activity. After harvesting _C. unshiu_ fruits on different dates in 2018, the peel was removed, freeze-dried, powdered, and stored at \(-80\)\({}^{\circ}\)C. The highest IC\({}_{50}\) values for the extracts (hesperetin, nobiletin, tangeretin, quercetin, and \(\beta\)CX) were observed in harvested _C. unshiu_ on Nov. 16 using the DPPH radical assay (8192.77 mg/mL) and the ABTS\({}^{+}\) radical assay (1181.56 mg/mL) [38]. The antioxidant activity of premature and mature _C. unshiu_ peel extracts were investigated in vitro. Premature and mature _C. unshiu_ peel were first dried at 80 \({}^{\circ}\)C for 9 h, ground with a blender into a 40-mesh size, and extracted with methanol (1:10 \(w/v\)) at 50 \({}^{\circ}\)C for 24 h. The extracts hesperidin and narirutin showed high antioxidant activity evaluated with five methods: H\({}_{2}\)O\({}_{2}\) scavenging activity, SOD activity, DPPH activity, ABTS\({}^{+}\) activity, and hydroxyl radical scavenging activity. Hesperidin and narirutin demonstrated higher hydroxyl radical and H\({}_{2}\)O\({}_{2}\) scavenging activities (74-98%) than the other tests [40]. Semi-continuous subcritical water extraction was used to investigate the antioxidant activity of bioactive components from the peel of _C. unshiu_. The peel was first dried for three days, ground into powder, stored at 20 \({}^{\circ}\)C, and then extracted with pure methanol for 30 min. Among active compounds, hesperetin exerted the highest DPPH activity (\(115.8\pm 3.9\) mg AAE/g), oxygen radical absorbance capacity (ORAC) (\(710.9\pm 12.0\) mg TE/100 mg), and ferric-reducing antioxidant power (FRAP) (549.1 \(\pm\) 21.1 mmol FSE 100/g) [44]. The antioxidant activity of _C. unshiu_ peel extracts in LPS-stimulated RAW 264.7 macrophages was assessed in vitro. The peel was ground into powder (100 g), lyophilized at 80 \({}^{\circ}\)C, extracted with 70% aqueous methanol for 24 h, purified, and then evaporated at 40 \({}^{\circ}\)C. Three compounds with highly antioxidant activity were isolated from _C. unshiu_ peel and identified as hesperidin, naringin, and rutin. These compounds significantly decreased ROS production and increased antioxidant enzymes (SOD, catalase) in macrophages [45]. Identification of bioactive compounds from _C. unshiu_ flowers and assessment of their DPPH activity were the objectives of an experiment. After extracting 195.0 g of extract from 3.2 kg of fresh _C.