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Large quantities of wastewater are discharged from natural rubber factory in the production process which contains about 0.1% of L-quebrachitol, an important natural optically active inositol which was used to treat diabetes in the local traditional medicine of Uruguayan and Brazilian. Because of the high extracting cost and hard up-scaling, the traditional methods of extracting L-quebrachitol were still at the laboratory stage. With the wastewater as raw material, the technology of large-scale extracting of L-quebrachitol was sought out by using membrane technology which was applied widely in recent decades, and dealing with this technology one patent was applied in the United States as well as in China. The output reached 10kg/a under laboratory conditions with a purity of 99.20%. The structure of L-quebrachitol was determined by elementary analysis, IR, NMR, MS and X-ray single crystal diffraction.
L-quebrachitol, Wastewater, Membrane technology.
L-Quebrachitolï¼ˆ1-L-(-)-2-O-methyl-chiro-inositol, figure 1ï¼‰is a kind of naturally optically active inositol which exists widely in the plant, and it has increasingly attracted as a chiral source in organic synthesis1-4. In Organism metabolismï¼Œit is mainly in form of phosphate ester or phosphate, and plays an important role as a second messenger, controls cellular processes by generating internal calcium signals4-9. At present, researches on synthesis of chiral inositol derivatives from L-quebrachitol have been widely carried out, and these derivatives would be used for antibiotics, antioxidant, enzyme inhibitor, inhibition of angiogenesis and diabetic treatment10.
L-Quebrachitol was first isolated from the Aspidosperma quebracho growing in South America and then found in several plants known as Eleagnus formosana, Maple, Allophylus edulis, Mitrephora vulpine, Hemp and Hippophae rhamnoides1,11-15. Though L-quebrachitol exists in many kinds of plants, the content is generally low. The rubber tree Hevea brasiliensis contains abundant L-quebrachitol. It can be isolated conveniently from the natural rubber factory wastewater which is the most industrialized valuable L-quebrachitol source2,10,16-17.
The rubber tree is widely planted in tropical and subtropical areas in the worldï¼ˆof the worldï¼‰. After development of decades, a quite mature industrial system of nature rubber has been established of which the industrial output value tends to be stable. In order to increase the output value of rubber industry, development of comprehensive utilization of the byproducts is(are) necessary. Undoubtedlyï¼ŒIt is an important way to extract L-quebrachitol from rubber factory wastewateråˆ©ç”¨æ©¡èƒ¶å·¥ä¸šåºŸ°æ-ç™½åšæœ¨çš®é†‡--æ˜¯å…¶ä¸ä¸€æ¡é‡è¦é€”å¾„. In this way, it can not only make use of the wastewater but also solve the problem of wastewater treatment. Although methods of(for) extracting L-quebrachitol have been reported in Some literatures17-19, They are still at the laboratory stage because of the high extracting cost and hard up-scaling.
Membrane technology is a novel separation technology which appeared in early 20th Century and developed rapidly in the decade of the 1960s. It is a new method of(for) separation(separating), purification(purifying), concentration(concentrating) under the action of an external force using a specially made film with selective permeability20. The benefits of membrane technology can be summarized as follows: energy consumption is generally low, separation can be carried out continuously, up-scaling is easy21. At present, it is widely used in industry of food, medicine, environmental protection, biological and chemical, etc.
With the wastewater as raw material, we isolated L-quebrachitol by using membrane technology instead of traditional evaporation concentration and column chromatography, and the output reached 10kg/a under laboratory conditions. The structure of L-quebrachitol was determined by elementary analysis, IR, NMR, MS and X-ray single crystal diffraction. The extraction method of L-quebrachitol has been applied for the United States and China patents22-23.
Figure 1. The structure of L-quebrachitol.
Materials and methods
General experimental procedures
Melting point was determined on a WRS-2 micro melting point apparatus and was uncorrected. Optical rotation was measured using a JASCO P-1030 automatic digital polarimeter. Elemental Analysis was determined on a Elementar Vario Micro cube. IR spectrum was measured on a Perkin-Elmer Spectrum 65 infrared spectrometer with KBr pellet. ESIMS spectrum was recorded on a Lcq Classic mass spectrometer. NMR spectra were recorded in DMSO on a Bruker AVâ…¢600 spectrometer with TMS as the internal standard, and chemical shifts were expressed in δ values (ppm). The X-ray single crystal diffraction data were collected using Mo Kα radiation (λ = 0.71073 Å) on a Bruker Smart 1000 diffractometer.
Extraction and Isolation
The wastewaterï¼ˆ40kg ï¼‰from natural rubber factory was heated up to boilï¼Œthen floating glue and flocculate were skimmed offï¼Œafter that the wastewater was filtered to eliminate the solid impurities while obtained clear liquid(34kg). macromolecule soluble matter such as protein in the clear liquid were removed by microfiltration membrane with 0.1μm micropore. In order to eliminate more soluble impurity, two ultrafiltration membranes were applied respectively which the molecular weight cut off (MWCO) were 5000Da and 1000Da. Then the ultrafiltrate (25kg) was concentrated to 3kg by nanofiltration membrane with 150~300Da MWCO. 480g of pasty material was obtained by vacuum distillation after decolorization by activated carbon (30g). Crystal was collected using cooling crystallization after 12h and then recrystallized for three times in 75% alcohol to get crystalline white powder of L-quebrachitol (42.5g, 99.20% yield). m.p.194.1~194.3â„ƒ; [α]20D -81.55 (c, 5.00, H2O); IR(KBr)cm-1: 3338.34, 2939.40, 2928.68, 2901.93, 2882.60, 2835.40, 1139.33, 1102.89, 1086.36, 1078.17, 1063.54, 1048.64, 1015.16; Negative ESIMS: m/z 193.00 [M-H]- ( Calcd for C7H13O6-)ï¼›Anal. Calcd. for C7H14O6: C 43.28, H 7.19; found C 43.30, H 7.27. 1H NMRï¼ˆ600 MHzï¼ŒDMSOï¼‰ d 3.11(dd, j=9.6, 3.3Hz, H-2), 3.31(m, H-4), d 3.32(s, H-7), 3.38(m, H-3), 3.44(m, H-5), 3.69(like q, H-6), 3.87(like q, H-1). 13C NMRï¼ˆ150 MHzï¼ŒDMSOï¼‰d 57.5(C1), 68.52(C1), 70.96(C5), 72.53(C6), 72.70(C3), 73.78(C4) , 81.58(C2).
Results and discussion
Wastewater from natural rubber factory has complex components containing large amount of proteinï¼Œlipoidï¼Œpigment and about 0.1% of L-quebrachitol. Membrane technology can be carried out in a continuous process, it was first applied to isolate L-quebrachitol from the wastewater for impurity removal and concentration. The crude extract was recrystallized three times from aqueous ethanol [ V ( ethanol ) : V ( water ) = 3 : 1 ] to give the refined product in 99.20% yield.
L-Quebrachitol was isolated as crystalline white powder. The IR spectrum of L-quebrachitol showed absorption bands at 3383cm-1 and 1015 cm-1 due to hydroxyl and methoxy groups. The 1H NMRï¼ˆ600 MHzï¼ŒDMSOï¼‰ spectrum exhibited signals of one methoxy group at ï¤ 3.32 and six carbohydrate anomeric protons(ï¤ 3.11(dd, j=9.6, 3.3 Hz, H-2), 3.31(m, H-4), 3.38(m, H-3), 3.44(m, H-5), 3.69(like q, H-6), 3.87(like q, H-1)). The 13C NMRï¼ˆ150 MHzï¼ŒDMSOï¼‰ and DEPT spectra exhibited seven carbon signals, including one methyl (ï¤ 57.5) and six methines (ï¤, 68.52(C1), 70.96(C5), 72.53(C6), 72.70(C3), 73.78(C4) and 81.58(C2)). From the above data , the compound was considered as L-quebrachitol1,12. The crystal structure of L-quebrachitol was determined from(by) the x-ray diffraction data, and solved by direct methods and refined by full-matrix least-squares optimization of F2 over all unique reflections (SHELXS-97). The ORTEP diagram of L-quebrachitol appears in figure 2. The crystal data for the structure determinations is given in Table 1. It crystallizes in a monoclinic system, space group P21, with cell parameters are a = 6.624(2) Å, b = 7.193(3) Å, c = 8.687(3) Å, β = 90.634(5) o and Z = 2. The ring is in chair conformations.
Figure 2. ORTEP diagram of L-quebrachitol.
Table 1 The crystal data for L-quebrachitol
C7 H14 O6
Crystal system, space group
Unit cell dimensions
a = 6.624(2) Å ï¡ = 90°
b = 7.193(3) Å ï¢ = 90.634(5)°
c = 8.687(3) Å ï§ = 90°
413.9(2) Å 3
Z, Calculated density
2, 1.558 g/cm3
Reflections collected / unique
24000 / 5641 [R(int) = 0.0443]
Goodness-of-fit on F2
Final R indices [I>2sigma(I)]
R1 = 0.0272, wR2 = 0.0589
R indices (all data)
R1 = 0.0291, wR2 = 0.0595
The membrane technology was first used for extracting of L-Quebrachitol, and production efficiency improved significantly and It can be large-scale extracting. The application of this technology also provided a feasible research direction for rubber factory wastewater treatment and recycling. We believe that the wastewater after the treatment by the membrane separation technique can be used in the production process of natural rubber. The water quality whether have an impact on rubber quality still requires(needs) further research.