In line with the revival of interest in the herbal remedies known from the ancient medical systems, such as Greco-Arab, Ayurvedic, and Chinese, there is also greater research activity in these medical systems particularly on the biological and molecular aspects of medicinal plants. As discussed in later chapters, there is an increasing trend in the United States and Canada as well as in Europe to incorporate herbal- derived remedies as an essential component in the medical curriculum. As a result, conventional medicine is now beginning to accept the use of herbal remedies once their efficacy and safety are scientifically validated.
Despite drug discovery technology diversification and reduced funding for natural product-based drug discovery, natural products from plants and other biological sources remain an undiminished source of new pharmaceuticals. 
The World Health Organization (WHO) estimates that about 80% of the world population presently uses herbal-based medicines for some aspect of primary health care. Although industrial funding for natural product-based drug discovery has been declining from 1984 to 2003, the percentage of natural product-derived small molecule patents has remained relatively constant. A comprehensive review of human drugs introduced since 1981 suggests that, of 847 small molecule-based drugs, 43 were natural products, 232 were derived from natural products (usually semi synthetically), and 572 were synthetic molecules. However, 262 of the 572 synthetic molecules had a natural product- inspired pharmacophore or could be considered natural product analogues. Natural products continue to make the most dramatic impact in the area of cancer. From 155 anticancer drugs developed since the 1940s, only 27% could not be traced to natural products, with 47% being either a natural product or a direct derivation thereof. The above analysis did not include biologics and vaccines, which are, by definition, derived from nature.
The use of, and search for, drugs and dietary supplements derived from plants have accelerated in recent years. Paralleling and even exceeding the growth in popularity of Arab and Islamic herbal medicines is the surge in information available to the public in the media. For example, a Google search using the term “Arab herbal medicine” reveals more than 280,000 citations. Faced with this huge amount of information, people are often left with a desire for guidance and direction. In the past decade, there has been an increase in scientific research activities in the Arab–Islamic world. Pharmacologists, microbiologists, botanists, and natural-products chemists are investigating the pharmacological properties of potential plants in order to identify phytochemicals and leads that could be developed for treatment of various diseases. A Medline and Google Scholar search using the terms “Arab herbal medicine” reveals more than 6000 citations. Examples include the use of traditional Arab and Islamic herbs for treatment of diabetics (1500 citations), cancer (1300 citations), liver diseases, inflammation (1200 citations), and infertility (1400 citations).
According to recent surveys, there are about 450 medicinal plants in the Eastern region of the Mediterranean and about 230 medicinal plants in the coastal Mediterranean region in Egypt. These plants are used by healers for the treatment and prevention of almost all types of human disease (Tables 9.1 and 12.1), such as cancer; skin, respiratory, digestive, and liver diseases; diabetes and others, and are sold or traded in market places in the Mediterranean region or internationally. In many cases, plant extracts are prepared into a mixture (Table 12.2). Plant parts used include leaves, flowers, stems, roots, seeds, and berries. In the following section, we discuss the efficacy of herbal remedies that are prepared according to knowledge of Greco-Arab herbal medicine in the treatment of human diseases, such as diabetics, cancer, infertility, and inflammation.
Most herbalists acknowledge that pharmaceuticals are more effective in emergency situations where time is of the essence. For example, elevated blood pressure posing imminent danger. However, they believe that over the long-term herbs are helpful in treatment as well as in prevention of diseases, and that in addition, they provide nutritional and immunological support that synthetic drugs or purified herbal compounds lack.
Herbalists generally use the whole plant or extracts from parts of plants, for example, the roots or leaves, but do not isolate a particular active compound. Modern medicine prefers single ingredients on the grounds whose dosage can be more easily quantified. They argue that the different phytochemicals present in herbs will interact to potentiate therapeutic effects of the herb and reduce side effects. Potentiation can be defined as positive interactions that intensify the potency of a bioactive ingredient. Additive and synergistic effects are subsets of potentiation, where two or more compounds in a mixture interact to provide a combined effect that is equal to the sum of the effects of the single molecule (additive) or where combinations of bioactive substances exert effects that are greater than the sum of individual molecules (synergistic). Potentiation can exist between two components in a single plant extract, two components from two different plant extracts, or between a phytochemical and synthetic drug. A good example of the multicomponent nature of botanicals is illustrated in the field of cancer research. Phytochemicals have been shown to affect various parts of signal transduction pathways including gene expression, cell cycle progression, proliferation, cell mortality, metabolism, and apoptosis. Combination chemotherapy has been the mainstay of cancer treatment for 40 years. It is therefore reasonable to assume that a mixture of compounds (phytochemical or synthetic) would have greater bioactivity than a single compound because a mixture of bioactive compounds has the ability to affect multiple targets. Studies have documented synergistic anticancer effects of phytochemicals including quercetin, catechins, resveratrol, and curcumin with various cancer drugs and/or other phytochemicals. In addition, natural products have been shown to overcome multiple drug resistance in tumors when used in combination with other natural products or drugs. Similar observations have been made in the field of antibiotic research. A number of plant extracts and natural products have been shown to work synergistically with existing antibiotics, restoring antibiotic activity against resistant strains of Staphylococcus aureus (methicillin resistant), Escherichia coli, and Shigella.
Human diseases are multifactorial and may be treated by consuming the chemical defenses that herbalists believe to be present in herbs (see Chapter 12). Viruses, inflammation, nutrition, and ROS (reactive oxygen species) may all play a role in cancer. Herbalists claim a single herb may simultaneously address several of these factors. In short, they view their field as the study of a web of relationships rather than a quest for a single cause and a single cure for a single condition.
In selecting herbal treatments, herbalists may use forms of information that are not applicable to pharmacists. Herbalists contend that historical medical records and herbals are underutilized resources.
As discussed in details in Chapter 16, the selection of potential medicinal plant in the Greco-Arab and Islamic medicine was based on the following factors:
(1) Knowledge developed traditional healers in the pre-Islamic period based on a long history of trial and error.
(2) Theoretical and practical knowledge introduced by Islam. These include natural products mentioned in the Holy Qur’an or in the Hadith of the Prophet Mohammad (Peace be upon him), for example, honey, milk, dates, black seeds, olive leaf, and olive oil.
(3) Theoretical and practical knowledge developed in other medical system, which became available to Arab-Islamic scholars after the translation of Greek, Indian, and Persian scripts.
(4) Theoretical and practical knowledge introduced by Arab and Muslim scholars. In the case of diet therapy, food built a substantial part of pre-Islamic medicine as well as in other traditional medicines, for example, Greek and Ayurvedic.
Diet is a matter of faith in Islam, and plays an important role in maintaining healthy body, soul, and spirit, which in turn strengthen the nature of their mutual relationship. The Prophet Mohammad (Peace be upon him) used food more than 1400 years ago. The Prophet also recommended regarding food as part of an overall holistic approach to health and incorporating into one’s everyday diet. Muslims should follow a set of dietary laws outlined in the Qur’an, were almost everything is permitted (halal), except what God specifically prohibited (haram). These facts may explain the remarkable outstanding interest of the Arabic-Islamic world in food therapy.
