**5. Designing a promiscuous multitarget inhibitor against three metabolic enzymes (alpha amylase, tyrosinase, and hyaluronidase)**

In principle, we hypothesized the following:


Based upon this hypothesis, we have developed in FAB-Lab luteolin-7-O-α-Lrhamnoside, which could be used as a potential multitarget enzyme inhibitor (promiscuous inhibitor) for alpha amylase, tyrosinase, and hyaluronidase.

Luteolin-7-O-α-L-rhamnoside could be used as a potential multitarget enzyme inhibitor in another words, promiscuous enzyme inhibitor, for the possible treatment of various health disorders such as angiogenesis-related disorders.

Luteolin aglycone, when compared with its glycoside, can easily access the catalytic site through 3<sup>0</sup> and 4<sup>0</sup> -hydroxy group in ring B (bonded to Cys83) and the 7-hydroxy in ring A (bonded to Gly245, Ala246, and Val248). These data are in agreement with other reports in which luteolin was proven to be a noncompetitive tyrosinase inhibitor.

While luteolin glycoside(5-O-β-D-glucopyranoside) could also be interacted close to Cu and HOO ions as kojic acid and L-tyrosine, luteolin aglycone and luteolin glycoside (7-O-β-D-glucopyranoside) could not. These findings support that sugar moiety at 7 position may have a role in the type of inhibition (i.e., noncompetitive).

Luteolin as a free aglycone has a very weak inhibitory activity toward hyaluronidase in comparison with luteolin-7-O-α-L-rhamnoside. This may refer to the importance of the hydroxyl groups in the rhamnose moiety at 7 position, and this was confirmed by the molecular docking simulation. Because there are two hydroxyl groups that bind to the amino acid residues Asp292 and Ser245 via hydrogen bond interactions.

There were not any reports about luteolin-7-O-rhamnoside inhibitory activity toward the three metabolic enzymes of interest.

In conclusion, more than 50 extracts of different medicinal plants were screened for their biological activities as inhibitors for some metabolism-related enzymes. Extracts with the highest activities were fractionated, and four compounds were isolated, which were found to be multitarget inhibitors for alpha amylase, tyrosinase, and hyaluronidase or at least two of them. Virtual screening and mechanism of action determination studies were performed also for these compounds.

### **6. Pharmaceutical and therapeutic applications**

#### **6.1 Liver research (liver fibrosis, liver cancer, interferon inducer)**

Establishing *in vitro*, *in vivo*, and preclinical models for liver fibrosis, liver injury, schistosomiasis, iron-overloaded, fatty liver, and immunosuppression, FAB-Lab team showed that naringin (a flavanol isolated in FAB-Lab grape fruit) exhibited a potent hepatoprotective activity [40]. Recently, it was further prepared in a nanoscopic nanomicelle formula to improve its efficacy and bioavailability as antiulcer and anticancer [41]. The prepared formula showed a very good activity in protection of gastric mucosa and suppressed the release cytokines *in vivo* model using ethanol-induced ulcer in rats. Moreover, in *in vitro* cytotoxicity assay using cell lines and EAC-bearing mice, naringin nanomicelle showed an excellent result as cytotoxic and tumor agent. This may prompt us to propose naringin nanomicelles as a nanodrug with prolonged release and enhanced antiulcer as well as antitumor activities [41].

#### **6.2 Colorectal cancer, human breast carcinoma, triple breast cancer**

Even though many flavonoids proved their efficacy in different models/assays against colorectal cancer, no solid evidence was about the relation between SAR

*Research on Natural Phenolic Compounds in FAB-Lab: Nonconventional Industrial… DOI: http://dx.doi.org/10.5772/intechopen.101446*

(Structure-Activity-Relationship) and colorectal cancer. This prompted the FAB-Lab team to examine the SAR of flavonoids and *in vitro* anticolon cancer using human colon cancer cell line (Caco-2). Surprisingly, the obtained results showed that the OH of C-5 and C-7 in A ring increasingly improved the anticancer effect of flavonoids when compared with 5-FU. In contrary, the presence of glucose moiety or OHd groups in B ring drastically reduced the anticancer activity. In conclusion, FAB-Lab team proposed a novel, hypothesis SAR of flavonoid-colorectal cancer therapy, which may provide a new horizon to better improve management of colorectal cancer [42].

#### **6.3 Antimitotic activity**

Several natural phenolic anthraquinone compounds were isolated from different plants and agriculture wastes in FAB-Lab. The salient features and the different biological activity of various anthraquinones compounds depend mainly on the distribution of OH groups in the basic skeleton. The study in FAB-Lab revealed that the presence of OH-group at O-position is a very important feature to portray a potent antimitotic activity (Badria assay) as seen in alizarin, which is the only OH-quinone having an OHd group in an ortho-position. The SAR study revealed that other compounds were active but in the following orders: emodin > aloe emodin > rhein > quinzarin. Interestingly, our results showed that 1-hydroxyanthraquinone could be a carcinogen [43].

Gingerol, a natural phenolic compound, and its derivatives exhibited a broad spectrum against different cancer cell lines and could be also used as a chemosensitizer with currently used anticancer drugs [44].

Ricinine, a simple alkaloid isolated from castor seeds in FAB-Lab, was used to prepare 16 derivatives and tested against SAS-oral cancer cell line in MTT assay versus 5-FU as possible agents for treatment of oral cancer. Sixteen new analogues were synthesized from ricinine. In contrary to 5-FU, the ricinine derivatives were able to suppress the growth of cancer cells at 25 mM [45].

#### **6.4 Cataract**

Phenolic compounds from both ginkgo (GK) and olive leaves (OL) extracts were examined both in *in vitro* and *ex vivo* assays against aldose reductase to find potential and selective inhibitors for the enzyme and possible use as a preventive or treatment for cataract. The promising results prompted FAB-Lab team to reveal the possible inhibitory mechanism of GK and OL by using computer-assisted programs. The results revealed that the phenolic compounds could inhibit the polyols pathways via halting the advanced glycation, which may have a crucial role in pathogenesis of cataract [46].

#### **6.5 Idiopathic nephrotic syndrome**

Phenolic contents of lyophilized *Citrus paradise* (grape fruit) were prepared in standardized soft gelatin capsules (GF) in FAB-Lab. The prepared capsules (GF) were coadministered with cyclosporine (CsA) for patients diagnosed with idiopathic nephrotic syndrome in Nephrology and Urology center at Mansoura University, Egypt. The coadministration of GF capsules resulted in increased CsA exposure in the range of 10–25%. Moreover, this clinical study proved that CsA-GF coadministration

was found to be safe and well-tolerated as confirmed from laboratory and clinical studies [47].

#### **6.6 Iron chelation (curcumin, mangiferin, catechins)**

Catechins (from green tea leaves), curcumin (from turmeric rhizomes), and mangiferin (from mango leaves) were among many other phenolic compounds that had been isolated in FAB-Lab [48, 49]. Iron-overload disorder (hemochromatosis) is one of the major reasons of morbidity. Most of the commonly available iron-chelating agents suffer from many side effects, which pronounced the need for a safe and effective natural iron-chelating agent(s) alternative. Therefore, FAB-Lab team conducted several *in vitro* and *in vivo* studies on selected polyphenol compounds (catechin, curcumin, and mangiferin), which may serve excellent natural alternative for commonly synthetic iron-chelating agents. Different iron-overloaded experimental models were conducted and disclosed the high efficacy of catechin, mangiferin, and curcumin (as shown in **Figure 5**). Subsequently, three very promising alternatives could be used in both clinical and industrial iron-overload or oxidative stress health and/or environmental problems [49].

#### **6.7 Antiviral activity**

Several formulae using proniosomes technique were proposed in FAB-Lab to prepare nanocurcumin (NC) as possible antiviral antiherpes (*Herpes simplex* type I) agent in comparison to a commonly used acyclovir (ACV). The results showed that NC exhibited a better and safe activity over ACV against Herpes-simplex Type I. Interestingly, NC-ACV combination reduced the toxicity and enhanced the efficacy that led to 100% plaque reduction over ACV alone [50].

#### **Figure 5.**

*Chelation of iron by catechin from green tea leaves (A), curcumin from turmeric rhizomes (B), and mangiferin from mango leaves (C).*

*Research on Natural Phenolic Compounds in FAB-Lab: Nonconventional Industrial… DOI: http://dx.doi.org/10.5772/intechopen.101446*
