**1. Introduction**

#### **1.1 General statement**

As any other organisms on Earth, plants are said to possess multi-functional properties. They constitute feedstock materials to feed people and are reputed for their uses in medicines [1, 2]. History of plants has been always related to that of Human. Reports said Human have always insured their primary health care by using plants [3–5]. Even with the discovery of technology leading to synthetic drugs with sometimes more efficiency, plants still remain ubiquitous and safe for health concerns.

Research currently overflows in the literature related to the chemistry and biology of plants. Interests focus on experimental validation of ethnopharmacological uses of certain herb and formulation of plant extracts for a sustainable health care [1–5]. Therefore, plants are ground, exhausted and evaluated for various biological activity including properties to inhibit the growth of or to kill microorganisms and tumor cell lines. However, both microorganism and cancer cells become more and more resistant and remain serious threats for life. As an example, resistance to penicillin used for the treatment of lung infection ranged from 0 to 51% around the World and between 8 and 65% *Escherichia coli* associated with urinary tract infections presented resistance to ciprofloxacin, another antibiotic (https://www.who.int/health-topics/antimicrobial-resistance). WHO took some measures to diagnose and eradicate the issue but the problem is still actual and present.

More than half of existing antibiotics and anticancers are from synthesis of which almost a quarter takes its origin in natural substances isolated from plants, marine organisms and microorganisms [6]. Nevertheless, plant supply extracts continue to play a relevant role in human beings daily life. Up to date data show that plant extracts are reputed in food science where they are used as dietary supplements [6–8]. This practice is prevalent in Europe and North America where the interest in plants and related materials is rising up. Despite the progress made in the field of the synthesis of active principles for the formulation of medicaments, people still rely on natural occurring drugs due to their safety and uniqueness. The list of valuable substances from plants cannot be exhaustive.

In ancient time, the discovery of salicin, an *ortho*-*O*-glucopyranosylphenylethanol, from *Salix alba* led to the development of the reputed anti-inflammatory agent aspirin [9, 10]. Morphine, a benzylisoquinoline alkaloid isolated from *Papaver somniferum*, is a painkiller quite known in medicine and which also exist under its derivatives, heroin and codeine [9, 10]. Another alkaloid namely quinine isolated from *Cinchona succirubra* has been for long employed to cure malaria and fever related ailments but since 2004, almost all antimalarial drugs in the markets is made up of artemisinin isolated from the Chinese medicinal plant *Artemisia annua*. Artemisinin is commercialized under various acronyms including arteether, artesunate or artemether [10, 11]. In other hand, the chemotherapy of breast cancer uses the drug taxol which is the commercial name for paclitaxel, a diterpene isolated from *Taxus brevifolia*. Other compounds like ingenol-3-angelate, from *Euphorbia peplus*, known under the acronym Ingenol mebutate or the L-histidine-derived alkaloid pilocarpine found in *Pilocarpus jaborandi* are also some drugs used against other form of cancer [12–14].

Days after days, we keep discovering the deeply wealth of our surrounded nature. Reports abound in the literature especially on valuable natural compounds in drug development [6–8]. Most of them highlight natural product scaffolds as building blocks to the development of other compounds through synthesis [6–8]. A list of priority backbones has even been proposed to lead the development of new drugs [6].

However, interest in health care could also be to find out natural occurring compounds with considerable effects and low toxicity which can be introduced in the actual pipelines of treatment of a disease. That is, the sensibility of the found natural substance is not strong enough to compete commercial drugs but could be proposed alongside prescribed medicines because of its safety and availability. This can actually help in low- or middle-income countries to face certain diseases and build up a sustainable health care system. One can question how useful was the discovery of artemisinin for indigenous people if they have to wait years for pharmaceuticals companies to manufacture the drugs before its consumption. The same interrogation can also be valid to other discovery from plants, e.g. taxol,

michellamine B or vinblastine. The plant sources of these active substances are known but still people from villages are waiting for "modern medicines" to take care of their respective health problems.
