Kinetic and Thermodynamic Study of Extraction of Oleoresin Containing Curcuminoids from Turmeric (Curcuma Longa L.)

Numerous studies are nowadays undertaken across the world laboratories on turmeric and show its excellent virtues in various fields such as medicine, pharmacology, cosmetics, and so forth. In this paper, to enlarge the domain of scientific knowledge, a kinetic and thermodynamic behavior of curcuminoid extraction from Curcuma longa L has been investigated in the dilute medium using ethanol as solvent under a magnetic stirrer. Through the KUNYIMA method, by means of the KUNYIMA first law, the global kinetic constant has been calculated at 250 rounds per minute (rpm) and the data have shown its Constance at 500 rounds per minute at the same temperature (27.5 °C). The kinetic constant can serve to build a commercial tank of production of curcuminoids using the sizing factor to endow the Democratic Republic of the Congo with its home technology of curcuminoids extraction as is hereby discussed. Extraction enthalpy and entropy have been calculated in a closed system using the Arrhenius relation. The results of enthalpy indicate that the extraction of curcuminoids is an endothermic phenomenon. This endothermic behavior of the extraction of curcuminoids in ethanol under a magnetic stirrer probably suggests the predominance of the enol form of curcumin in presence of its tautomeric ketone form. Also, the extraction of curcuminoids in ethanol is an endothermic phenomenon and this last phenomenon probably suggests its non-bioavailability. The energy promoting solubilization of curcuminoids arises from the solvent, under a magnetic stirrer, that can meet its alike with the hydroxyl group (like dissolves like). The value of the variation of entropy has evidently suggested the disturbance of the natural order after extraction. Note that KUNYIMA's second law has been hereby announced.


I. INTRODUCTION
Nowadays, much research performed in laboratories has shown interest in turmeric plants in diverse fields. Experimental studies have been intensified since 2002 on turmeric to understand its multiple mechanisms of action. Indeed, in 2002, Inano and Onoda studied the radioprotective action of curcumin extracted from turmeric longa Linn: inhibitory effect on the formation of urinary 8-hydroxy-20deoxyguanosine, tumorigenesis, but not mortality, induced by gamma-ray irradiation [1].
In 2005, Reddy et al. published-on curcumin for malaria therapy [2]. The same year, Notarbartolo et al. studied the antitumor effects of curcumin, alone or in combination with cisplatin or doxorubicin, on human hepatic cancer cells [3]. In 2006, Cui et al. published that curcumin inhibits telomerase activity in human cancer cell lines [4]. The same year Hong et al. published their work on the effects of curcumin on the invasiveness of prostate cancer in vitro and in vivo [5]. In 2007, di Mario et al. published an article on "A curcumin-based 1-week triple therapy for eradication of helicobacter pylori infection: something to learn from failure" [6]. The same year, John et al. talked about curcumin for chemoprevention of colon cancer [7], Kowluru et al. studied the effects of curcumin on retinal oxidative stress and inflammation in diabetes [8], Li et al. published "Curcumin, a dietary component, has anticancer, chemosensitization, and radiosensitization effects by down-regulating the MDM2 oncogene through the PI3K/mTOR/ETS2 pathway" [9]. In 2008, it was the turn of Gaurisankar et al. in Anti-cancer effects of curcumin: the cycle of life and death [10]. The same year, Patel et al. published "Curcumin enhances the effects of 5-fluorouracil and oxaliplatin in mediating growth inhibition of colon cancer cells by modulating EGFR and IGF-IR" [11]. In 2014, Li et al. published on the chemopreventive activity of turmeric essential oil and possible mechanisms of action [12]. In 2015, Zhou et al. studied the essential oil of curcuma Wenyujin, which inhibits osteogenic differentiation in ankylosing spondylitis [13]. In 2022, Kunyima et al. published an article on "Anti-myocardial infarctus, efficient anti-poison and anti-prostate mighty spicy miscellany" [14]. The list is not exhaustive. The turmeric studies revealed that curcuminoids would prevent cancers (colon, lung, prostate, kidney, liver, skin, stomach, leukemia, oesophagus, etc.) and may contribute to their treatment. Turmeric treats stomach ulcers and inflammatory diseases (rheumatoid arthritis), relieves liver troubles, reduces hyperlipidemia and the risk of cardiovascular diseases; treats gingivitis (gum disease), prevents diabetes of type 2, and decreases the inflammation among diabetic patients suffering from nephropathy. Turmeric would improve the cognition performance in Alzheimer's patients (research is going on). The inflammation of the skin and wounds can be also treated with turmeric. In a recent publication [14] Kunyima et al. showed the healing power of spicy miscellany based on turmeric. We are convinced that many things remain unknown about curcuminoids despite abundant literature.

A. Materials
Ethanol 96 % has been used as a solvent.

B. Methods 1) KUNYIMA Method, KUNYIMA First Law and KUNYIMA Second Law
KUNYIMA method is a reasoning procedure consisting of apprehending a phenomenon, to try to mathematize it which means to express it in a mathematical equation. This equation is then solved, and the solution is tested by experimental. When this solution is verified by experiments, it becomes a law. In the case under study that means the extraction of curcuminoids in ethanol as solvent, it can be done massic balance sheet. Indeed the instantaneous variation of quantity is equal to the inlet massic debit of curcuminoids in turmeric minus the exit massic debit of curcuminoids from turmeric [15]. This corresponds to Equation (1).
To understand (1), it may imagine the quantity of oleoresin containing curcuminoids entering the turmeric (i) represented by the first term and the quantity of oleoresin leaving the turmeric towards solvent (j) represented by the second term. The first term is zero, the extraction begins with the total quantity of oleoresin containing curcuminoids already formed inside turmeric. There is no entrance. There is only the exit of oleoresin by extraction. This corresponds to Equation (2).
kij is the kinetic constant when the oleoresin containing curcuminoids leaves the solid state (i) towards ethanol (j) as a solvent and for the rest, it will be written only k. Considering the oleoresin containing curcuminoids as a unique compound, the addition sign (Σ) disappears.
* : is the extractable mass of oleoresin containing curcuminoids in ethanol in (gr) * : depends on the polarity of the solvent, its polarizability, its refractive index (properties of solvent) : is the conversion (extracted mass of oleoresin containing curcuminoids at time t) * : is considered as a constant in each solvent and at a given temperature.
Equation (12) is the work equation. For the rest, we use: = 1 Thus, Equation (12) becomes Equation (13). KUNYIMA method allows us to establish (13). as there is no intercept here. When the second form of (12) is used, the intercept is  Indeed, (13) has been successfully tested by experiments in the case of extraction of Gourd seeds oil [16], Moringa seeds oil [17], Sesame seeds oil [18], and now in the extraction of oleoresin-containing curcuminoids from Turmeric in ethanol. It is the reason why the laboratory has decided to call it KUNYIMA first law, to honor Dr. Anaclet Kunyima Badibanga, chairman of Lacopa-PCC, who gave this elegant tool to undertake the extraction studies in a dilute medium. Now it becomes possible for researchers to undertake a kinetic and thermodynamic study of the extraction [19] as it will be likewise shown in this paper in the case of extraction of oleoresin containing curcuminoids in ethanol.
KUNYIMA's first law can take the following form: * is constant.
,-# = Where v is the extraction velocity or massic velocity (massic debit) in For the study in title, k is the global kinetic constant of oleoresin and all the curcuminoids. It will be expressed in (s -1 ), (min -1 ), and (h -1 ) if the extraction time is in second, in a minute, or in hours.
If the extraction concerns a compound of well-defined chemical structure, KUNYIMA's first law can be written in a concentration expressed in molarity. It becomes KUNYIMA's second law. That means:

C0= extractable concentration in in solvent
Ce= extracted concentration at time t.
KUNYIMA second law has been successfully also tested in the case of curcumin as it will be shown in the next publication. This second law can take the form (20).

2) Determination of the Volume of Extraction Reactor Vr by Means of Kinetic Constant k and Conversion Rate g : Sizing Factor
In this paragraph, we want to solve the timeless problem of the transfer of technology and endow the country with its' home technology. The volume of the extraction reactor depends on the desired quantity of materials it is needed to be produced. It is shown below how to build an extraction reactor knowing kinetic constant k and conversion rate (g). The chosen example concerns the determination of the volume of a closed continuous stirrer pilot tank (reactor) from kinetic constant ( ) and conversion rate (g).
The mass balance of a reactant can be written in a general form applicable to all types of reactors. For a time element dt and a volume element dv, the general form is shown in Equation (21).
The first 2 terms represent the mass of reactants entering and leaving the reactor during time dt. The 3rd term depends on the rate of the reaction (interaction) applicable in the volume element dv. The 4th term expresses the resulting change in mass of reactants during the time dt caused by the 3 other terms. The 3rd term can be of the form Γ ∨ ∆t where Γ represents the rate of disappearance of the reactant per unit volume.
Consider the simple case where there is a feed flow and a product flow. The properties of these flows do not change with time. The 1st and the 2nd term of the above equation of mass balance are constant and are equal to the flow velocity of the masses of reactants multiplied by dt. Remember that there is only interaction.
Let F be the mass flow rate of the reactants and γ ; the conversion to feed. The mass of reactant entering the reactor is shown in Equation (22).
The mass of reactant leaving the reactant volume element is shown in Equation (23) where γ > is the conversion at the output. As the reaction (interaction) of the mixture is at uniform temperature and composition, the reaction (interaction) rate is constant and can be evaluated at the temperature and composition of the product. Let Γ be the reactant conversion rate.
The mass of reactant converted into a product will be Γ ∨ ∆t . Assuming there is no buildup of reactant mass in the reactor, the equation of mass balance becomes: This expression can be used to estimate the volume of the reactor required to produce a given conversion γ E and to know the conditions F and γ ; . The reaction (interaction) rate is constant in the reactor. To evaluate it is necessary to know the temperature of the product.  is the volumic velocity (volumic debit).
A has been called the sizing factor. If the sizing factor and the desired volumic debit (Q) are known the minimum volume of the reactor can be determined. Now the specialists can give the desired form to the reactor by determining its diameter, its length if it has a regular form. The reactor must work at the same temperature where k has been determined and in a similar environment. can be determined in the following way:

3) Thermodynamic study of curcuminoids
The global kinetic constant of oleoresin containing curcuminoids is determined in a closed system, the Arrhenius relation can be used to assess the values of extraction enthalpy and extraction entropy.
The experiments have been performed in a closed system at temperature and pressure constant.
The energy calculated is

4) Extraction protocol
Natural turmeric rhizomes have been bought at the Kinshasa market, dried at 50 °C, and afterward ground. One gram of turmeric powder has been placed in the cartridge. This cartridge has been placed in a flat bottom balloon flask containing a magnetic stirrer and 100 ml of ethanol as solvent. The thermometer has been placed in a balloon flask orifice to control the temperature that must be constant during all the experiments (27.5 °C) in the lee of light. The balloon flask endowed with a magnetic stirrer with its content has been placed on a heating agitator to be stirred at 250 rpm during a certain time. At each stirring time, the solvent (ethanol) has been removed from the mixture by means of a spin evaporator (mark Hei-VAP 1.0) programmed at 79 °C for ethanol for 20 minutes at 80 rpm. Afterward, the balloon flask has been placed in a drying oven at 80 °C for 10 minutes and cooled in a desiccator before being weighed in order to determine the extracted mass of oleoresin-containing curcuminoids. At each stirring time, the experiment has been repeated in exactly the same condition. The experiment has been also performed at 500 rpm.

III. RESULTS AND DISCUSSION
As it is shown in Table I (likewise for the following tables) each value of the extracted mass of oleoresin containing curcuminoids at 27.5 °C and 250 rpm is a mean value of three measures, the mean error has been used to express the precision of the measures. The precision (∆me) on the difference (mo-me) has been calculated by the logarithmic method with mo constant. Likewise, the precision of the massic velocity (Table II and Table IV) has been calculated by the logarithmic method considering mo and k constants. Assuming that the extraction of turmeric rhizomes by ethanol or acetone gives 6 -10% of oleoresin containing 35-45 % of curcuminoids [20] and these latters are responsible of turmeric's characteristic yellow-orange color while the essential oil contributes to its aroma and its typical flavor [21], it is shown in Table I     According to the Origin Program 9.2, the value of the global kinetic constant has been assessed at (0.1597 ± 0, 0012) min -1 in the above-evoked work conditions. This global kinetic constant suggests the facility with which the oleoresin with its content is extracted by ethanol, it is somewhat a measure of solubility of the curcuminoids in ethanol.  Table II gives the evolution of massic velocity as a function of extracted mass (me) of oleoresincontaining curcuminoids at 27.5 °C (250 rpm). In Table II, the evolution of massic velocity (v) with the increase of extracted mass of oleoresin with its content (me) in ethanol can be observed.
The decrease of massic velocity has been evidenced without surprise at 27.5 °C in accordance with (18), suggesting the ethanol saturation in curcuminoids for a given sample as it is shown in Fig. 6.
The experiments have been also performed at 500 rpm as it is shown in Table III. Table III shows the evolution of the extracted mass of oleoresin with its content in ethanol as a function of stirring time maintaining temperature constant and the closed environment constant except for the magnetic stirrer velocity now at 500 rpm. It can be observed in this table the increase of extracted mass of curcuminoids at each stirring time until it remains constant to allow the calculation of mo found to be (0.4515 ± 0.0003) gr as indicated in Fig. 7.
Applying KUNYIMA's first law the global kinetic constant has been found practically the same as it can be seen in Fig. 8 (k ═ 0, 1597 ± 0, 0001) min -1 . This result suggests that the global kinetic constant of extraction of oleoresin-containing curcuminoids in ethanol depends on temperature and environment. When the temperature is kept constant and in a given solvent, the global kinetic constant remains constant. The same kinetic constant has been found. Mass velocity has been also investigated at 500 rpm as indicated in Table IV.    In Table IV, it can be observed the evolution of massic velocity (v) with the increase of extracted mass of oleoresin with its content (me) in ethanol. The decrease of massic velocity has been also evidenced without surprise at 27.5 °C in accordance with (18), suggesting the ethanol saturation in curcuminoids for a given sample as it is shown in Fig. 9.
It should be noted here that Fig. 6 and Fig. 9 have of course the same slope. What is the physical meaning of the value of massic velocity appearing in the last column at time zero as well at 250 rpm as at 500 rpm while the extracted mass (me) of oleoresin containing curcuminoids is zero, the extraction has not yet begun? This value which arises from the definition of massic velocity (18) can be explained as a potential massic velocity obtained by extrapolation, not yet in action. It will be in action when the extraction begins with the contact of ethanol with turmeric powder. So it has been decided to write this value with an asterisk in both Table II and Table IV. This value of the global kinetic constant of oleoresin-containing curcuminoids together with the conversion rate γ can be used to size a closed continuous stirrer pilot tank (reactor) means to determine the reactor volume if the desired vulumic debit (Q) is known using the sizing factor (41). Note that the global kinetic constant (k) and the conversion rate (γ ═ 37 %) are determined here at the same temperature (27.5 °C) and in the same environment.
Let us take for example γ calculated by   Equation (61) can be used as it is shown in Table V and Fig. 10.
There is a linear relation between reactor volume and desired debit in both situations (250 rpm and 500 rpm. The calculations of extraction enthalpy and extraction entropy are hereby discussed. The values of ∆H and ∆S have been also calculated. The value of ∆H shows the presence of endothermic phenomenon. This endothermic behavior likely suggests that the solvent with hydroxyl group receives the energy from magnetic stirring and makes possible the solubilization of its alike (like dissolves like), which means in ethanol the enol form of curcuminoids is predominant compared to its tautomeric keto form.
With respect to the positive value of entropy variation, it suggests merely the natural disturbance of the system after the extraction of curcuminoids. The physical meaning of mole in units of ∆H and ∆S is difficult to imagine because the measure has been done on mass of oleoresin containing curcuminoids, material of unknown well defined chemical structure. Nevertheless, this value of ∆H is equivalent to the energy (power) beared per mole to induce extraction or to promote solubilization and its corresponding entropy. The real value of those parameters will be calculated when the compounds of oleoresin will be determined.

CONCLUSION
The establishment of the KUNYIMA first law and the announcement of the KUNYIMA second law bring the scientific revolution in the field of solid-liquid extraction. KUNYIMA's first law and KUNYIMA's second law are elegant tools to undertake the kinetic and thermodynamic study of curcuminoids extraction in closed systems or only kinetic study in an open system. The kinetic constant is a measure of curcuminoids solubility in ethanol. This study has allowed confirming the predominance of the enol form of curcumin in ethanol as a solvent.
The extraction of curcuminoids in ethanol is an endothermic phenomenon and this last phenomenon probably suggests its non-bioavailability.